The native quest resolution is approximately 1832×1920 per eye or 3264 X 1920 (both eyes). I'm going to basically promise you Steam is automatically scaling up your SS to 150% because it doesn't know how to properly scale newer HMDs in newer games unless the devs tell it what to do. I know for a fact SteamVR tried to do this to me (Odyssey) . Set it to your native resolution (100%) and I bet your problems melt away.

I guarantee you cannot run 5000X3000 in most other modern, AAA games without some reprojection. Trust me on this one. If for no other reason than other people are running Squadrons on a 3080 with no problem, even on similarly specked HMDs.