I don't think higher cpu clocks make that much difference after a certain level if you are driving a monitor. It might perhaps help in career missions where you can encounter lots of a.i. driven planes.
I recall on my old system getting over 3.6GhZ was what made a difference. Big, high-res. screen performance is obviously a gpu thing but for VR a high clock speed makes all the difference. Going from 4 upto 4.6 gives me an appreciable difference. As did turning off hyper-threading.
However, there is a lot that can be done in game too that really helps it along.