Try locking the game at 60 fps, messing around with threading in the launcher, and resolution, make sure edit mode isn't on, don't leave the "control T" cheat on, if it is. There has been issues reported with mouse speed and fps on the campaign menu as well for some users in warband, I occasionally get slowdowns on the campaign map (not as severe as yours) but keeping the game locked at 60- or 80 fps and 3k has lessened the impact, that's for warband, mods, vc, modded or otherwise.
Im not really able to give a definitive answer as others have had these issues going back over a decade and the solutions are varied, sometimes is a directx issue, sometimes mouse lag, sometimes a redownload fixes it.
It's not really about what my pc can handle as I can run games like 2077, KCD, Bannerlord etc at high-ultra ish, warbands a bit old, a bit wonky, and build before all of our tech. VC really stresses the capability of warband, I hope you can get it figured out because it's a game I have spent 900+ hours in and not really slowing down.