fyi you can use the deck restore image on an amd build, although probably there will be complications
https://help.steampowered.com/en/faqs/view/1b71-edf2-eb6d-2bb3#reimage
afaik chimeraos is the recommended alternative, which is a fork of the current steamos, with more supported hw (but not nvidia)

had you installed mint or pop, you could just install multiple chrome variants from the software manager

it definitely is more user friendly, i remember trying ubuntu 10+ years ago and the default driver was awful, the nvidia driver install ran in the terminal and asked questions that i had no answer to, so half the time i fucked it up, and then it didn’t support my monitor so i had to edit the x server conf to get the correct resolution and refresh rate. and when the new drivers came out i had to re-do everything every time
for a few years now you just install with a usb stick and everything runs great

check out the protondb page, maybe something helps
(filter for the appropriate gpu and distro but the latter is less important) https://www.protondb.com/app/212200

idk which mmo it is but i would assume an older engine runs more reliably on linux than a new one

actually, for me, trying and failing to run star wars republic commando a few years ago on win 10 was what pushed me to really look into gaming on linux, and after installing it via steam, enabling steam play, i just clicked play and it ran great, i was shocked
and you can add any windows executable to steam (although it’s a bit janky), enable compatibility, and most of the times, stuff just runs
heroic launcher also is great, but a bit more complicated

why do you need to switch? win+p is the switch between mirrored and joined mode right? why not just let the system handle it?
i too have a few consoles and i use a hdmi switch before monitor 1 and on the 2nd monitor i sometimes switch between hdmi and vga for an older pc, but i just let pop do whatever

what’s “ate”? edit: oh it’s just a type for “are” isn’t it

i would recommend getting an extra ssd, installing a beginner friendly distro (mint or pop for instance) and just boot it up occasionally, see what works, what doesn’t. i got into linux like this, gradually, over years