Monitor not outputting full 180hz on external display; other refresh rates are slow as well

[glomar_response]

See if this post helps.

What is the most recommended process to downgrade the NVIDIA drivers to get Starfield working under Proton in Garuda?

There is no particular recommended way to downgrade nvidia drivers or any software due to the fact that if you downgrade a particular software and it is making deprecated API calls to libraries that no longer support those calls due to the fact that the rest of the system and other libraries are going to keep updating. This is going to cause issues if not immediately it is definitely going to do so in longer run. This is why even on archwiki it says to implement a snapshot subsystem and try to …