Hi!
so do you want to create a video with good quality or do you want to have a better quality in the game?
For video recording: Shadowplay doesn't have enough mbits for really good videos. I use fraps which is heavy on your hardware but if you have a good PC it works fine and has the best quality you can get without an extra recording hardware!
If you want to have a better quality in the game:
First thing to use would be 8x MSAA.
Content manager can enable it or you can change a few lines in this ini:
documents\Assetto Corsa\cfg\video.ini
"AASAMPLES=8".
If you want to use supersampling you could use VSR (amd) or DSR (nvidia). Just google around for it
But this will scale your apps to be smaller...
What works better and what I use (only nvidia) is "Sparse Grid Super Sample Anti Aliasing" (SGSSAA).
You need the nvidia inspector for it, go to the AC profile and do this:
But you will have to disable smoke in the game as it will get supersampled too and my GTX1070 goes down to 20fps instead of 80fps