The only other standard advice I see for running flight sims concerns Windows 10 Gaming settings. The advice is to switch Xbox Game Bar off and also Game Mode to Off.
I didn't realise you were running 4K and the GPU card is probably not as well optimised for this resolution. You could try a lower screen resolution to start with using high or ultra to see if you can get to +50FPS. Once there you could increase the res and see if this still gives you acceptable FPS levels. I am pleasantly surprised by what I have been able to wring from this GPU. It also supports VR very well.