I myself played few mods even tried BWP and really enjoyed it but there are some mods that i probably didn't try because there is so much mods for Baldur's Gate that it is really hard to know each mod. That is the main reason for this thread.
we can divers in 2 ways BG:EE mods and old BG1/2/tutu/BGT mods
old BG1/2/tutu/BGT mods SCSII: great mod for improving AI and other aspects of tactical combat with enemies in baldur's gate especially mages
old BG1/2/tutu/BGT mods TACTICS: many great TACTICAL improved encounters/enemies in BG2 with really hard combat (at least for new players) but sometimes can be a little cheesy