When FSR is enabled on Bottles' settings, it sets environment variables and arguments for both Wine and Gamescope, which means that if you use a Wine version that supports FSR (like GE) and Gamescope, you are getting two separate instances of FSR, which is not how it's supposed to be used.
In theory, you could simply give priority to Gamescope's FSR, since there is no need to check whether the Wine version supports it. However, Wine-GE enables FSR by default, because due to the nature of the hack, disabling it causes problems (related: #2636). Thus, the right logic should be "if both FSR and Gamescope are enabled, don't enable it for Gamescope if the Wine version supports FSR".

There's more: some settings conflict with each other, like FSR's "Quality Mode".
This is a Wine-exclusive feature (I'm implying Wine-GE), set with WINE_FULLSCREEN_FSR_MODE: what it does is forcing a different set of resolutions of a game, plus the native one. It has two problems:

• If you use a Wine version that doesn't support FSR, and instead use it via Gamescope, then this setting does nothing, and Bottles doesn't communicate it.
• If you instead use a Wine version that supports FSR, it conflicts with Gamescope's game resolution: setting both of these will crash the game at the start¹.
  Bottles' UI should clearly communicate what is enabled given the other settings and what is not. How should this be done (for this specific example)?

So, solutions?

• Just remove FSR's "Quality Mode", and get the problem out of the way.
• Don't care if a setting is silently doing nothing.
• Reorganizing somehow the settings so that what is enabled and what is not is clearly communicated.

So, that's why I'm opening the issue.

(By the way, Wine has WINE_FULLSCREEN_FSR_CUSTOM_MODE (not implemented in Bottles), which adds a custom resolution in the resolution list. This however does not conflict with Gamescope.)

Related: #2755.