This game sure does stutter a lot. What a shame. It's another case of not knowing if I should just blame my outdated PC, but for what it's worth, I do get over 120 fps on these settings in this same area if I disable the frame rate cap. Also, it's interesting that MangoHud continues reporting a solid 60 fps while this is happening. Of course I forgot to enable to frame timing graph for this recording, but I did try running the game with the graph enabled while not recording, and the stutters didn't seem to register there either. The graph looked even smoother than in some games where I can't perceive any such issues. So I don't know what the fuck. I'm certainly not prepared to blame Linux or Proton, because I remember the game being somewhat like this when I played it on Windows (although, to be fair, I think that was on an even older PC than this one).
If it is just a case of my PC still being shit, then I can probably blame either the CPU (which is now the bottleneck since I upgraded only the GPU because of the old one not being well supported anymore), or the fact that the game is running off HDD storage (and maybe this stuttering happens when things are loading). But it could be a problem in the game itself. I've seen this happen in other games over the years, but rarely to the extent that it annoys me as much as in this one.