The game can crash a crazy amount of times too, leaving fights takes forever sometimes, literally up to 15s-20s after completing a normal mob it’ll take to transition back to Tidus, & it can corrupt & destroy your save file(s).
Certain cutscenes would just become green screen with audio but no picture, so bright it hurts your eyes. You are still able to get Steam Achievements iirc, however there are a lot, & I mean a lot of issues that could arise from the mod.
I don’t know much about other mods, but I have used the FF X Project one.