(This laptop, mind you, is a low spec sub-$200 (at the time of purchase) laptop. In fact, its specs are low enough that I wouldn't run modern Windows on it, even if I were a Windows user (I'm not).)

Of course, I do have a couple questions:
1. Should I buy the DLC with the 15% discount? Also, how big is the DLC (file size), and can one choose not to play with the DLC if it's installed? Or should I wait until I plan to actually play the game? (Currently, I'm planning on replaying Bard's Tale 2 DOS.)
2. In testing to make sure the game works, I discovered that enemies get experience when they hit your characters. Does this ever actually come into play? In other words, does an enemy leveling up (or the possibility of such) ever have a strategically significant impact on the gameplay?

I'm afraid the gog-community isn't exactly active. If you have a steam-account, there is much more going on there.

Regarding your questions, the file size of the DLC is 76MB. Given the small size you can easily (de-) install it if you want to/don't want to use it. I guess you can switch between DLC and no DLC via galaxy, but I don't use it so I can't tell for sure.

DLC can be activated during the campaign, but I doubt that it can be deactivated again without strange things happening.

I enjoyed the DLC very much as it integrates well into the already great base game. Of course, the last part is a highly subjetive opinion ;)

I'd say the price for the DLC is maybe 2,- if you compare content and cost of DLC vs.base game.
But than again the base game is very cheap for what it is offering, so I didn't hesitate.

If you like stuff like FFTA, Tactics Ogre, Shining Forces or (to a lesser exted) Fire Emblem you should have fun with Fell Seal as well. Gameplay is polished, quite a bit to min-max if you are into that but you don't have to grind. Difficulty can be tailored to your liking and you will have to prepare for each battle carefully on the higher settings. The normal setting is pretty casual. The story is allright for one campaign but nothing exceptional.

Enemies do level up during combat, but it only matters (somewhat) during the first encounters. Later on it's much more important which abilities/class combinations the enemy has and what kind of equipment they are wearing. Those things are dependent on the enemies' level, but don't change during a fight.


Ps:
I think I recognise your nick from some other rpg-Forum (Pathfinder? Wizardry? M&M) and if you happen to share my taste for tactic-rpgs as well, you will have lots of fun with this game :)

Unfortunately, that slight discount ended well before you replied, and it does not make sense to buy something at full price that I am not going to play right away.

Currently, in case you're curious, I am currently playing Bard's Tale 2 (DOS), and have been experimenting with a few different set-ups (in particular, having casters that skip to advanced classes rather than learning all the spells first), and I currently have other games I am looking at:
* Final Fantasy 5 with Project Demi (a hack that supposedly shortens/removes cutscenes while leaving the gameplay intact)
* Some games from that one itch.io bundle with 1700+ items in it

As for this game, it's more the character building possibilities and the DLC's monster recruitment that made me interested in the game, not the tactical combat (I prefer Wizardry/Dragon Quest style combat, actually). (I have played Final Fantasy Tactics and Disgaea, though I didn't quite beat the former (though with Orlandu + Math Skill it wouldn't have been a challenge), and the latter I beat the main story and some extra stuff but I don't think I beat Baal.) At least is isn't real-time-with-pause, however. (If it were, I wouldn't have considered this game, as I found that combat system to be the worst of both worlds.)

You might have seen me on the Wizardry and Might and Magic subforums, but not on the Pathfinder ones.