Ok, so your LOD is probably too high. You can use the fps dev tool to ensure your mainthread latency stays in the yellow.
For a reference, I have a 10700k @ 5.1 all-core, and 200 LOD is as high as that CPU can go before I get so mainthread limited that I get stutters.
Start with reducing your LOD, on the ground at the busiest airport you fly at, until the little yellow bar on your mainthread stays yellow. If you’re getting more than a tick of red every couple of seconds, your LOD is too high.
Once that is set, increase the load on your GPU until your render latency is as close to 30-32ms as possible.
You might have to increase render scaling to get the latency up that high. This will allow your CPU time to think between frames, and prevent stutters.