Terrain Object Shadow options are Flat, Default or Off
I see no change from one to other: -10+ fps and increase in GPU frametime.
Further testing: Only option to regain 60fps and loose the stutter is to turn off shadows and terrain object shadows... which leave the cockpit awash with light and zero life.
Turn off that repro-garbo and try your G2 at 60Hz. You may be among those of us fortunate enough to not see the 60Hz flicker.
If so, crank those settings and enjoy.
I will add, don't plan to use the WMR portal built in to Steam. Use it stand alone. This way, when you're testing and launching the rest, you won't even need to have Steam open at all.