I have 7800X3D, RTX 4090, 32 GB too and can confirm similar behaviour on my system.
It seems RAM is always fully used. I also found that if I fly at low altitude over forest trees, the performance gets worse.
I get typically around 30 - 45 FPS in VR on a Q3, but the problem is I get stutters every few moments when the FPS drops below 36 FPS (I run the Q3 at 72/2) as it needs at least 36 FPS to run smooth. For the moment I stopped using FS2024 and went back to FS2020. It runs at higher visual settings solid 50 - 70 FPS in the same flying situations.