Also an i9 10900 and RTX 3080 user here, and I don’t want to tease but my experience is vastly different. At almost 4k (I have a super wide 1.4k monitor almost equal to 4k in pixels), I get in simple planes and not heavy areas at least 50-60 FPS all day long. For the heaviest of airports and airliners, I will still pull 30-35 the least to date. Never ever I seen my FPS drop into 20s yet with this new system. And all this in ULTRA/max out and render scale of 100 to match my 3444x1400 monitor. Heck, I have two of these monitors and I expand the window at 1.4k resolution to make it 6888x1400 total (way more than 4k) and STILL I run 30fps for heavy scenery and all ultra. What is more important though is your FPS in vanilla scenery flying, randomly in the sky: If you don’t get there 40+ no matter what you fly, something is wrong sorry.
This goes to say to NOT give up as it is NOT ok to have just 30s FPS with such GPU and CPUs… do anything it takes, but know there is tons of power left to be given there…
Good luck.
I did the standard stuff like disable game mode, tune nvidia settings for performance, etc.