Some mods, UI and audio mods in particular, have been broken as par for the course, I don't know about UI mods but audio mods are trivial to fix;
officially the devs are okay with mods that don't alter the gameplay, although some mods (such as the one for loadouts idr the name) that use scripts got caught in the crossfire

No, since the game launched they were using GameGuard. Today's patch replaced it with EAC