

Using Proton 8 the game launches with its default 30fps cap in place with perfect frame times.
Fullscreen disables 30fps cap
Valve recommends Proton 7.0-6, but in my experience this version of proton breaks the 30fps cap, either by unlocking the game entirely or by adding constant stutter so I dont recommend this version. Toggling the ingame fullscreen option may also break the 30fps cap, unlocking the game speed and making the game run way faster than it should. Use the performance overlay to make sure your game is running at 30 and you shouldn't have any issues.
set PROTON_USE_WINED3D11=1 strangle 30 %command% in launch option
and do use Proton 5.0-10 Because anything newer than 5.0-10 doesn't work with the launch option.
wouldn't start on the correct screen
The game is tied to fps and I couldn't find a way to limit it to it's prefered speed (30fps)
Game requires adding PROTON_USE_WINED3D11=1 %command%
to start as Margriff mentioned, however, the strangle part didn't work and wouldn't allow the game to run. Without that, the game runs far too fast and since the gameplay is tied to fps, nothing really works
Without using Wine D3D it staggers at 12 fps and it's really annoying to play
With Wine D3D, game works fine... well... with 55~60 FPS, but game is intended to be played at 30 FPS, so it just moves too fast...
To fix this, you must install libstrangle [https://github.com/milaq/libstrangle] (just follow install instructions) then, in steam, add to initialization options: PROTON_USE_WINED3D11=1 strangle 30 %command%
Wine D3D will make game run faster than it should, so you use libstrangle to limit game's fps to 30, and everything works just fine!
The game's speed is tied to FPS. SteamPlay makes the game run above the intended 30FPS, making everything move too quickly.

Out of the box, the game runs poorly. Unless the graphics settings are lowered to "Low" the game can run so poorly that too many inputs too quickly can cause a crash. Tweaking runtime options to disable D3D11 seemed to help just enough to prevent crashing long enough to get to gameplay, but not enough to make the game practically playable. Even with tweaks FPS is low - 10-15 normally, occasionally lower - and crashes are frequent enough that the game can be described, at best, as "technically" playable.

Runs extremely poorly, 10-15fps at best. Slows down whole computer.

Runs very well, though with quite a low FPS.