For anyone running Bazzite or SteamOS-like distros on anything more powerful than a Steam Deck, set SteamDeck=0 in the launch options like I have. The game reportedly has a hidden Steam Deck specific profile that gets enabled, which seems to result in more pop-in and lowers the graphics. If you are already running the game like this, then the shader cache generated by the game at first boot needs to be removed. There are guides on how to do this, but the easiest way is to backup the prefix in case your saves are gone and remove the original prefix.

Additionally, install DLSS-Enabler for non-Nvidia systems for XeSS or FSR support, which looks a lot nicer than the built-in TAA and TAAU options. However, FSR3 frame generation via DLSS-Enabler does not work properly with the HUD however, and enabling HUDFix disables generated frames despite the FPS counter due to how the game renders the HUD.

The game launches in windowed mode on my window manager (Niri). Messing with the resolution options other than native resolution seems to be somewhat problematic, but using something like Gamescope seems to resolve it, especially with my problem of the game launching windowed and not fullscreen.

I recommend installing FF7RebirthFix to run the game in aspect ratios other than 16:9 and with a framerate cap above 120FPS.

Using gamemoderun and setting my GPU's performance profile to high seems to fix any problems. Alternatively, just run something like the below to get the same result manually.

echo "high" > /sys/class/drm/card0/device/power_dpm_force_performance_level