Apparently 200% render scale in PC settings does wonders for VR performance

[CptLucky8]

@HyperJet2018

you see that for example the menu will only be shown in the HMD and not on the monitor.

This is because these are using a dedicated VR only API for presenting popup textured quads into the VR view (overlays).

It is because they are independent of the whole frame rendering, that I suggested using these for higher legibility of the EFIS screens among other things:

[BUG/FEATURE] EFIS Screens Problems and Solutions for higher legibility - Virtual Reality (VR) / VR Wishlist - Microsoft Flight Simulator Forums

This would let you use lower rendering settings for the outside view with higher res popup overlays in-lieu of the EFIS screens VC polygons. This would also decouple the sync between the whole frame rendering and the EFIS rendering which can in some cases open up other optimization opportunities.