Specifically in BG TOS. Considering a fighter/thief for my first game, just don't know if their restrictions still allow for fun and balanced gameplay. Any tips for that multiclass?

'Balanced' is a subjective word when it comes to games. They are balanced in my opinion, and they are fun to play. You may want to consider what your party makeup will be, though. For example, if you plan to take along your childhood friend Imoen, there is very little point in being a F/T, since she's the best thief in the entire game. Another example: if you intend to go the so-called 'canon' party (Imoen, Jaheira, Khalid, Minsc, Dynaheir) there is also little point being a F/T, but you ARE missing a cleric, so why not Fighter/Cleric? You also get one of the best weapons in the game to suit that character quite early on.

I agree with Hickory. BG can be finished and enjoyed with any kind of class as long as you know what you are doing. Wanna be a Fighter/Thief? Go ahead. Imoen rocks but you may want to dualclass her to a mage. This will render her thief abilities blocked until her mage class becomes 1 level higher than her thief class. You may benefit your thief skills during that time. Also, with the backstab ability of thief, you may sneak into the mob and stab their precious mage.

As a rule of thumb, a multiclass character with two classes will be one level behind in each of their classs compared to a single class character. So when a single class is at level 3, a multi will be at level 2/2, and so on. Depending what classes you're comparing it might not quite work out that neatly, and it starts to break down after level 10, as single class characters shoot further ahead. But as far as TOS is concerned, multi-classing is fine.

Dual-classing is a bit trickier, and if you really want the most of it you need to read up on the XP tables and the level cap. I'd save it for a later character, especially if you're looking at fighter/thief (the multiclass version automatically gives you the best level spread).

In my experience:
Fighter/anything is probably good.
Cleric weapons are at odds with backstabbing, so thief/cleric isn't a great choice.
Triple class combos might be fun at first level but they get to be a drag pretty fast.

Actually, I could point out that:
1. You can backstab with staves and (I believe) clubs, so you do have options for that purpose. (I believe you can also backstab with Spiritual Hammers.)
2. There is some synergy with this combination: Draw Upon Holy Might raises the caster's Dexterity, which will in turn improve your thief skills.

In fact, in BG2, for every class combination, there is some synergy that makes that combination unique. Some of them don't apply to BG1, unfortunately (like Cleric/Mage synergy that relies on the ability to put cleric spells into sequencers, which don't exist in BG1.)

IMO multiclass characters are balanced apart from fighter/mage, which is overpowered, and on the other hand triple-class fighter/mage/thief or especially fighter/mage/cleric which really struggle to get enough experience for all three classes.

The classes in BG aren't balanced at all. Which is a good thing, really. A high level wizard should be way more dangerous than a high level thief etc.

That's what I like about the game. When it comes to balance 2nd edition D&D rules is out of !@#$s to give. I don't agree with your thief example though. I use thieves and druids to counter mages. Mages are very squishy, making the thief more likely to one-shot the mage with a backstab (don't forget to use non-detection).

Fighter/thief works very well in the game, this hybrid class is far more powerful than pure class thief.

All races work for this class, I recommend maxing strength, dex, con and cha, the other stats aren't important. I'd roll for a stat sum of 89+ which will allow 10 int and 7 wis for cosmetic reasons on top of racial maximums in the other stats.

Very important is weapon specialization, bows and longswords (allow backstabbing) are good candidates.

Ignore the spoilers about party makeup, play your own game. Planning ahead will most likely lead to walkthrough hugging and frustration, you don't know who's out there, if or when you meet and how you will like them.

I am talking about what they can physically do. For practical purposes. Delivering a good stab should be easier to do (require less XP) than using magic to make a meteor strike your enemies. Mages need more XP to get to, say level 20. But when they do they can wipe the floor with a pile of level 20 thieves.

Why? Remember that there is no real-world counterpart to magic, and magic works differently in different fantasy universes.

For example, in some settings it may, for many people, be easier to attack with magic than to deliver a good stab. In a common magic setting (one where being able to use magic is the default, and nearly anyone can), magic may be easier for nearly all people. (Case in point: SaGa Frontier 2, where nearly anyone can use magic, but being an assassin requires special training.)

This is a Baldur's Gate forum, which means that people are specifically referring to magic in the Baldur's Gate universe -- why must you always bring other games into it? Anyway, arcane spells in 2E require complex movements and gestures (somatic components), so Stig79 is absolutely correct that a simple back stab would be infinitely easier than an arcane spell.

"No matter how subtle the wizard, a knife between the shoulder blades will seriously cramp his style."

But, BG and BG2 mages have counters to that.

For BG:
Mirror Image provides complete protection against a number of attacks. As long as you have at least one image, damaging attacks *can't* damage the character. (This includes area attacks.) Note that there is no chance of hitting the real caster when there are images.

For BG2:
Mirror Image is less powerful here (as an attack *can* happen to hit the real mage, plus there's the issue of True Sight), but mages get a couple more options:
* Stoneskin negates a certain number of physical hits, no mater how much damage they would do.
* Protection from Magical Weapons provides complete protection against most enemies' physical attacks (at least those that are serious threats). Against the rest, there's Protection from Normal Weapons. (Note that a player would be able to deal with PfMW by switching to a non-magical weapon, but the enemies you face aren't that smart, and monsters whose natural attacks are counted as magical do not have this option anyway.)

So, with the "knife in the shoulder blades", we see the following possibilities if the wizard is prepared:
* Oops! That wasn't the real wizard! Try again!
* That skin of stone blocked the knife. Try again!
* Wait, why isn't this knife doing any damage?

You miss one of the biggest points of the thief: "if the wizard is prepared"

Sure, reality bending is great and all, but you can't do it forever, and you can't be prepared for everything at all times. One of the thief's easiest mage protection counters? Walk away and wait for the spells to expire.