The changes, as the others have indicated, are mainly in terms of AI and character building (you can use all the kits, for instance). But, EasyTutu has a number of
mods built for it (the BG2 engine is capable of doing more things than the BG1 engine. Tutu is thus more mod-friendly, as it utilizes the BG2 engine). If you install mods for it like the
BG NPC project , you should notice much more fully fleshed out NPCs, as well. The
Unfinished Business mod will install some components and quests that were never fully fleshed out in the game. There are a number of other quest mods you can consider, as well. There are a few NPC mods like
Finch and
Gavin, that will introduce you to modder created characters. Try those things out and you'll have a pretty different game experience.