I can vouch for terrible performance on 'high/medium' tier hardware. My similar specs being:
i7 7700
GTX 1080 8gb
32gb DDR4 3133MHz
HDD + SSD (used both, no performance difference)
Booting up Single-player is a little grainy with performance, a few lag spikes here and there as things render however this is normal and after I'd say 5-10 minutes of an instanced battle/roaming the map I reach 120-144 frames per second consistent at max settings.
Moving over to multiplayer, the performance is horrifying; consistent and frequent frame drops, lag frames, unsmooth animations and high GPU/CPU usage (typically at the 100% mark) ravages both my PC and my experience, absolutely terrible and as quite an enthusiastic Warband player with over 4,500 hours I'm left quite disappointed in the fact I can't have a genuine experience. All drivers are updated, decreasing graphical options actually WORSENS performance, all applications being closed, priority adjustment within both Task Manager, Process Lasso and Process Hacker have absolutely no changes.
This is 100% down to the poor resource management issued by the games code, no modern game (i.e Red Dead Redemption 2, Witcher 3, Escape From Tarkov) runs as bad as this on Multiplayer. Based off of the people I have asked, people with lower-end specifications actually run the game substantially better such as i5 6500 + GTX 1060 Supers.
Please focus efforts on the optimisation on the game because quite frankly it shouldn't have half the performance issues it is currently having.
- Just to confirm, multiplayer lobby size/player count/map/game mode does NOT influence the frame rate on Multiplayer, it is just iffy across the board.