I tried it now, and i must say: wow, you really nailed it this time!! Super great work! 
Thank you so much!
My preferred settings are:
a) without Reprojection:
OXR 100% Scale,
inGame: 100% Scale,
for your FS2020.cfg:
scaling=0.85
sharpness=0.0
b) with Repro:
OXR 90% Scale,
InGame 100% Scale,
for your FS2020.cfg:
scaling=0.7
sharpness=0.0
I see no FPS increase when running at the same render Output Resolution. But with same Resolution i see a better image quality than the Upscaler built into MSFS. Especially less flickering of Trees! The Key is to have inGame Resolution to 100% and let your NIS Plugin do the upscaling.
I am also happy that it works with Reprojection!!
This time you made it possible that the Resolution displayed to MSFS gets reduced, perhaps a FOV option could be included? Then the resolution in MSFS would get even smaller and your code would scale up and has to leave black edges (which us G2 users with goggles cant see). I think this would result in FPS gain which could also be traded to cranking up the scaling.
But even without this, thanks a lot for your effort 