I found more FPS to play with! (no real numbers but ~26 (60Hz) to ~43 (90Hz) - Caucasus/Solo/Day/Calm)
I fly VR only, at 60 Hz, and with all options set to lowest except Textures (Medium), Anisotropic Filtering (8x), Smoke (2).
Since the update I have moved to 90 Hz and changed Textures to High, Water to Medium, and Smoke to 4. Still very smooth, actually, even better than before. Additional option cranking induced stutter and frame loss but I didn't spend a lot of time experimenting
The haze is superb and makes the map come to life (even without shadows). I can now see distant objects instead of blurry smudges.
Unfortunately, too many CTDs; changing MSAA to 2x, flying in mutli-player, snapping head around quickly.