ME: All mods break save compatibility when installed mid playthrough
You: But only mod X breaks it via method Y

So whats your point? Who cares if its asset size or tlk table? installing a mod mid playthrough breaks your saves.

No it doesn't. Not if done right.

just because the save loads without crashing doesn't mean it didn't get corrupted.
If you are lucky then the corruption is somewhere where you never notice. but those can add up over time.

Also, how does one "do it right"?
only way I know is to know exactly what files each mod changes (as well as save file modifications) and about all possible incompatibilities and issues. Which is humanly impossible task
There is a reason all modders strongly recommend you not make any changes once you started a playthrough

You are talking in absolutes. "installing a mod mid playthrough breaks your saves" That is an absolute, and it is absolutely false.

Necro, I know, but I just thought of another.

You can only access certain areas of the map by exiting other areas heading a certain direction. For example, the only way I know of to access the farm area right beneath the entrance to Baldur's Gate is to exit the Bandit Camp heading West. It might also be possible to access the farm by exiting the Mines heading East. This had me stumped for a while.

This is something you perhaps discover on your own pretty quickly, by necessity or not, but...

Ranged Weapons (and kiting) is King!

very true, especially at low levels in BG1.
I played through durlags tower mostly with melee weapons, because my tank (khalid) had such a good AC that enemies hit him only with a crit. Because you can only have ammo stacks of 20, I had to retreat to town for buying more ammo although I filled most of my inventory with ammo. (This happened in cloakwood forest +mines)
I think you have stacks up to 99 in bg2 (I am not 100% sure) what makes ranged combat much better.

some general things:
- For Thac0, AC and saves lower is better, for everything else more is better. This has improved in DnD3, where more is always better.
- Importand stats should be as high as possible, others can be dropped to the minimum.

- use potions and spells to improve your party (buffs). Use wands and other items against enemies. Things are there to be used. This includes usable equipped items and the characters special abilities.
- What you should NOT do: In my first game my party attacked the enemy, the casters used only damage spells and I sold everything where I was not sure what it is good for. But I made it through the game somehow.
- Do NOT dispell yourself. When fighting a group of enemies I buffed myself for 1 minute and the first thing I used in battle was Keldorns dispell. It removed most spells on the enemy and myself. So my group was confused or afraid after some seconds though I used spells to protect myself from such things.
- Start the combat by backstabbing the enemy mage to death. With boots of speed this can be done even when they cast true seing. It can not always be done, but when it works the battle becomes a piece of cake. And it is fun to see how the mage´s protection spells trigger upon death.
- Always have a thief around to search for traps and scout the enemy.
- save often and in different slots
- Do not stand in the fire.
- non magic metal weapons can break in BG1

A more general - and very important - tip would be to know the 2e dnd rules in general, at least insofar as they apply to the game. You can find a short(ish) summary here. It looks longer than it is, because it contains a lot of charts which tkae up space.

1.) Knowledge of 2E will not always help, and will often hinder. BG loosely follows 2E, but institutes many house rules and implements snippets of 2.5 material to the point that it barely resembles RAW 2E at points, and the initiative system is wildly different from the Wasteland style of initiative 2E used. Knowing the linked rules that pi4t posted is definitely helpful, but do not make the mistake I did and assume that knowing 2E will provide you with the knowledge needed to survive.

2.) For the love of Bhaal, Lightning is dangerous; do not use it unless the caster takes point down a hallway with enough room to evade the bolt, or unless you are in the open, have immobilized the enemy, and can move out of harm's way.

3.) Mods are not always a good idea. The rings mod was definitely useful (seriously, why wasn't that part of the original game?), but TuTu had... issues. The swollen number of different types of proficiency resulted in things like Khalid, a diversified archer and axe/swordsman, suddenly turned into someone who blew all their proficiency points on bastard swords (formerly covered by their large swords proficiency) and two weapon fightig, despite having stats that made melee combat ill advised, let alone shieldless.

4.) Non-combat solutions are rarely, if ever, adequately rewarded. The few times that I was able to bluff my way past someone, I never noticed any experience being awarded; in a game like BG where gaining levels is the primary way to assure your survival (better HP, saves, etc.), that's rather problematic if you try to roleplay a character who tries to avoid direct confrontation.

5.) Sidequests are the focus, not the main plot. Sidequests provide the bulk of magic items and XP, more so than the main plot; ignoring them to follow the plot will result in you being underleveled and at an elevated risk of dying. As a result, if the sidequests don't do anything for you, there is no point in playing.

6.) The game cheats. When I got to the end, I always triggered a Dialogue with Sarevok, even though he could not have possibly seen my sneaking thief. After the dialogue, I always was hit by an AoE spell with no visible caster (casting negates invisibility) or trap triggered. Occasional railroading plot events is fine, but cheating to stack the odds against the player is not my idea of fun; as a result, I quit at that point.

7.) Do not play like in a PnP game. In a well run PnP game, the monsters will fight relatively intelligently, or failing in that, they tend to exercise tactics that go beyond "attack the first thing I see". In BG, the enemy AI doesn't even begin to fight back in a way that a DM would have them behave, with the only attempt to emulate a monster's sense of self-preservation being a morale roll. Also, most DMs will give you an idea of what you will hit with your spell/whether you are in range prior to casting; in BG, I have yet to discover a way to predict where a spell will go or whether I am in range other than guesswork.

8.) Sleep is awesome, even if it is altered from PnP. Fun fact: 2E sleep has no save under RAW.

Now I'm intrigued -- what kind of mod is the "rings mod"? A part of the tweakpack, do you mean the option where you can use several magical items, like magical armour AND ring of protection for example?

If so, this limitation is something that always frustrates me, because I'm often left with the choice of going with better AC (armour) or better saves (ring etc).

Point 4 is a bit frustrating too, and is done much, much better in Planescape Torment. I wish it was possible to solve quests in BG's world too peacefully, and still be rewarded for it. The way the games are designed, you are sort of carroted down the path of Good and always use force (perhaps ironically).

I wish these games had some proper reactivity, so choices you make now can have serious consequences way down the line.

The "rings" mod is a mod that causes jewelry and rings to stack; this is crucial early on when you need to hoard as many of them as possible to sell off, as in the unmodded version, a ring will not stack, which wastes many inventory slots. I'm not a fan of the "one AC altering item at a time" thing either; as far as I can tell, this was house-ruled in by the devs and does not seem to have any basis in 2E RAW (then again, 2E's defining characteristic is using the RAW as guidelines as opposed to hard and fast rules).

I made it through my first playthrough without rings stacking. I'm sure lots of people did. It is definitely annoying managing useless loot across multiple inventories just so you can sell it later. Eventually, I just stopped giving a crap about 3gp here and 10gp there.

Sorry, but your infinite ammo and the "ring mod" is nothing but cheating.
So the dicussion goes like this:
q: First try- What do you wish you knew?
a: The game is easier when you cheat (like giving yourself infinite amme or stack AC like crazy)

This is true, but it is not my idea of fun.
But why stop there? The game is much easier when you kill everything via console and give yourself tons of exp for it.

lets be serious again.
I finished the vanilla game (BG1 and 2) without any mods or cheats several times. I just finished BGT which improves some things but adds some new bugs. BGT removed the exp cap of BG1 (though I never wanted this) and there were 2 enemies that were so bugged that I had to kill them via console to continue. This was the first time I had to cheat and I hated it.

summary:
- When you play it the first time, use the vanilla game without any mods or cheats. It is possible. Get a party of 6 as soon as possible and give everyone a ranged weapon+ammo and a melee weapon. safe often and in different slots. You may die a lot, but the best way to learn is to try out different things until you succeed. Sometimes you learn that the enemy is too strong and you have to come back later.

EDIT:
Three more things not mentioned until now.
- Better armor does NOT reduce the damage you take. It reduces your chance of being hit. So when 2 chars (one naked, the other one in a full plate, everything else is the same) fight the same type of enemy, the naked char will be hit more often, but when they get hit both take the same damage.

- There is also a 5%chance that you hit and also a 5%chance that you miss, no matter what your equipment is or against what you fight. Same goes for the enemy. So there is a chance that your super equipped fighter misses a goblin and the goblin hits you. Most things in this game are determined by throwing a dice (a virtual one, its a random number generator i guess) and if you throw a 1 your action always fails and with a 20 it always succeeds.
This applies not only to physical attacs but also to several other things.

-When you do a critical hit you do double damage unless the target wears a helmet or is immune to crits because of other reasons. Same goes for enemies so WEAR HELMETS!

EDIT2:
- Do not think that the game rules make any sense.
Just imagine the following situations in the real world:

- There is a machine that throws stones at people. All stones have the same wight and the same speed. There are two people: One is naked and the other one wears a full plate mail. For the armored person it is much easier to evade the stones, but when a stone hits the armor, the person inside gets the same injuries as the naked person being hit.

- Two naked people fight each other with swords. One wears a helmet, the other one not. Both manage to hit some vital organs of the other one (like stabbing each other into the heart). But the one without helmet gets twice as much injured as the other one.

Nice rant there. Pat yourself on the back.