Better support for multihead sim racing

Feature Request

First of all, the Linux gaming community really appreciates all the work that has been done with proton.

Since long ago, the typical way for wine-users with 2 or more monitors to play with 3840/5760 screenwidth has been to enable the virtual desktop with desired screenwidth and change the game resolution with the in-game options.

Since proton 5.13(?) and the fullscreen hack and AMD fsr patch where added(unless Im mistaken with the latter) this way for extra screenwidth has not been possible.
It is possible to use proton 5.0, but this version is according to some users "slower" than the more recent ones, and sim racers and I often want to use the fastest proton.

Somebody requested a option to disable the FS hack in runtime, but my request is different in that multihead users, and the sim racing community still wish for the opportunity to be able to game on later proton versions.

I confirm:

• [ x] that I haven't found another request for this feature.
• [x ] that I have checked whether there are updates for my system available that
  contain this feature already.

Description What do you want to be added?

At the very least; offer config-instructions on github for building a customized, and functional proton with these hacks disabled.
This would kind of create two protons, but its cost-effective.

At the most; make proton work for both multihead users and single screen. Dont know if this would disable fsr_hack for all games though.

Justification [optional] Why integration in Proton instead of Wine?

This might be an issue for wine.

Risks [optional]

asteroid impact (joke, sorry)

References [optional]

No files, tests, or entry points are named. Start by reviewing the Proton 5.13-era fullscreen hack and AMD FSR changes referenced in the report, then determine whether the desired result is custom-build instructions or runtime support for multihead setups. Done would mean documented configuration or confirmed support for the requested multi-monitor resolutions.