I have exactly the setup you described, a Raspberry Pi with an 8 TB SSD parked at a friend of mine. It connects to my network via Wireguard automatically and just sits there until one of my hosts running Duplicati starts to sync the encrypted backups to it.
Has been running for 2 years now with no issues.
gamescope is a mess inside of Flatpak as of right now. Some issue with using Proton inside of gamescope inside of Flatpak.
I played Alan Wake 2 using the native Heroic version and native gamescope.
The gamescope version still needs to be pretty recent. After starting the game make sure its brightness does not change when you play with the SDR intensity slider. If it does, it’s not using HDR.
Also, Alan Wake is a pretty bleak looking game in general so you might want to pop some flares to bring some color for testing.