Try default Ultra settings
DX11
Frame rate limit - off
Vsync - off
https://forums.flightsimulator.com/t/dlss-functional/554167/6
Nvidia drivers are also important.
1 Download latest Nvidia GeForce Hotfix driver version 526.61.
https://forums.flightsimulator.com/t/new-nvidia-hotfix-driver-version-526-61-just-dropped/553823
2 Uninstall nvidia drivers via DDU
3 Install Nvidia hotfix without nvidia geforce experience