What I have come to realise with this game is that there is no one setting that will suit every situation you want to play. I can run 4K Ultra with no tweaking at 40-50fps in the countryside with an XCub no problem but a TBM over London will struggle with that (hello stuttering) so you drop to 4K High End and 40Fps is yours for the taking (or Medium if you want super smooth). Add On aircraft, like those from Cerenado, cost me about 8-10FPS so High End is the option of choice for those situations.
For this game, unlike, say Forza Horizon, I don’t think there is one setting configuration that will work for all circumstances and you have to choose your settings depending on location and the plane you’re using. The main difference between Ultra and High End appears to be a bit of sharpness close up and long range rendering of very distant objects. Even Medium looks good on a 65" screen in 4K.
What would be useful is an option to have Custom settings saved as presets and those presents be selectable from a button on the inflight menu system. Short of having an RTX 3090 inside a super tuned system I think that’s just the way this game has to be.