I’d suggest:
- you leave FS2020 2D Render Scale alone.
- you set FS2020 VR Render Scale to 100%
- you set SteamVR Refresh Rate to 90Hz
- you set SteamVR General Render Scaling to 100% (about 2000x2200 IIRC with the Index)
- you set SteamVR FS2020 Render Scaling to 126% at a minimum (about 2200x2400 with the Index)*
- you set SteamVR FS2020 FOV to 95% (no need for more really, and this contributes a little bit more to sharpening the views)
With this you’ll get good tradeoff between visuals and perf with FS2020, while leaving enough room (on a 2070S) to enable Motion Smoothing (fixed rate 18fps, 33ms prediction)
If you have better hardware, or if the 27th release gives more perfs on your system, I’d recommend you just raise SteamVR FS2020 Render Scaling to 152% at a minimum to get started with (cross check your steamvr.vrsettings it is actually using 150%)
If you can raise the bar further, try SteamVR FS2020 Render Scaling to 300%… You’ll get the entire view as legible as when using 50% FOV at 126%, which is really giving a lot of details (I change this quickly sometimes on final to get crisp runway visuals at a distance! - easy to do with the Index in using the HMD mounted button!)
For much more details:
My 2070 SUPER VR settings and suggestions (Index - SteamVR) 
- Virtual Reality (VR) / Hardware & Performance - Microsoft Flight Simulator Forums
*setting this to 126% in the SteamVR VR GUI Settings is effectively using 125% in practice!