The terrain level of detail setting.
In large photogrammetry areas, this setting tanks your performance as your CPU is loading in hundreds of small chunks at once. The setting is also somewhat exponential. Try going from 50 to 100 in London or New York, then go from 100 to 150. The performance loss will be greater on the latter.
You have to think of it like a radial area around your plane. Even though I have a very high end system, I generally avoid cities in faster airplanes because my 5ghz 9700k cannot keep up.
I believe every system is CPU limited in these places. Drawing in trees is almost completely handled by your GPU as they’re copies of the same sprites over and over (2d shapes). Which is why you see almost no loss in FPS from low to ultra.
This isn’t Asobo’s fault either. If I open up Google Earth and change my view to see in the distance, my system tanks too.
These are my full specs.
RTX 2080 / 9700k / 16GB RAM / 3500mb/s m2 SSD
I exclusively play in VR.
Oh and, people who say you need more RAM for this game, you really don’t. I select a SSD that MSFS 2020 isn’t installed on for my virtual memory. It’s not an issue.
CPU will always be the biggest bottleneck for this game, unless you totally avoid the more complex aircrafts and areas with photogrammetry.