The Barbarian large town is bad enough, lagging from time to time, especially as your army reaches the main square at the top of the oppidum. However, your city and large-city level settlement is untenable, unbearable, dropping frame rates left and right, throughout the entire siege. I played a siege that took an hour and a half just to finish (even though I've got a 45-minute time limit and didn't even use up half of my hourglass); that's unprecedented and quite unsatisfactory. Did you guys not draft any testers for this? I know from reading elsewhere that I'm not the only one to bring this up, either.
Unfortunately, your mod *forces* the player to play with high unit detail in the graphics settings. Otherwise various units, across multiple different factions, look absolutely haphazard, bugged out, missing eyeballs, capes, helmets, having completely wrong textures and colors. I've eliminated shadows and grass detail, put building detail on low, and put my filter on bilinear to compensate and improve performance/frames per second. In any other siege or field battle your mod plays just fine. When it comes to your Barbarian settlements, it's almost not worth the effort, with auto-resolve seemingly very tempting. That's a shame, because your Barbarian settlements look pretty cool.
In light of that, how are you going to fix this problem? Couldn't you just provide us with a lower resolution quality version of the large town and city settlements for Barbarian factions? Obviously you are doing something wrong with them if literally every other settlement model plays just fine.