It's best to think of the NWN1 engine as just a platform for online multiplayer, something to host community modules in, and coupled with being a Bioware game is why it's a very clunky game to play. It's especially notable how bad NWN can control at times when you compare it to KOTOR's engine for which NWN's engine was effectively a protoype. NWN2 is worse in comparison to NWN1 because of the shitty camera and some of Obsidians modificication of the engine and then rushes it out its games because Obsidian was just the studio you go to to get an obligatory sequel.
Is NWN1 better or worse platform for community modules? While I appreciate the fact that it is not as much of a rushed slop pile as NWN2 likely was at launch, if it's as much of a clunky mess, I might as well go for the newer version with a nice online class builder.
I own NWN EE, I just avoided it because it was BioWhore and after I booted it up and scoped it out, it seemed like a vastly worse experience compared to Infinity Engine. It's fucking hideous. I think I'd rather play Icewind Dale. Weirdly enough, NWN2 visuals aged much more gracefully. It doesn't look bad, surprisingly. The visuals are pretty decent when you pan out the camera.
Some time ago Nwn EE received updated that lets you see how aoe spells will hit by highlighting ground.
It was more so the fact that the AI seems to aggressively nuke my party members. Even if manually controlled, they seem to blunder around hopelessly and looking dazed and confused. I would regularly queue spells or attack actions with AI turned off, and they would sit there doing nothing. Their pathing regularly gets fucky and they provoke unnecessary attacks of opportunity. For some reason as soon as I turn AI on, my melee characters start running off aggressively in various directions, target swapping randomly.
For example, I would click on monster A to queue an autoattack, and they would immediately target swap and start running towards monster B, provoking an AoO from monster A and C.
The AoE targeting also seems to prefer "latching" the pie plate onto a primary target, meaning that anything around it gets nuked. If I can, I usually try to place the edge of the pie plate on the enemies to avoid friendly hits, but it can be cumbersome in some parts of the game where friendlies get deeply embedded. That's fine, and that's part of why I turned on friendly fire, but it's the latching behavior and characters getting stuck/running around randomly that made me kind of avoid using pie plate spells in most fights, or prefer things like chain lightning.
I don't remember much in the way of gamebreaking bugs. Except for maybe the Trial sequence, I think that could jam up badly but I never encountered it myself.
Specifically during the keep siege, when targeting the reaver with the scroll, I got some weird bug saying it was an invalid target, making it impossible to progress. I also had a few times where the world map doodad would bring up the party member but not actually take me to the world map selection screen, making it impossible to travel. A few crashes, mostly towards the end. Largely stable, though, mostly minor bugs due to collision/camera getting stuck when scaling steep ramps/cliffs.