Hello, just some feedback on my investigation.
I've discovered that if I use mpeg color range instead of YUV, my speed to render out to yuv420p/nvenc are same as shotcut (for reference purposes). Near realtime (10 sec video renders in 10 seconds with no edits). Colors of output video seem to be same as input. I've been using kcolorchooser and I cant find a diff.
I see in the manual, that 'mpeg' offers less color range than jpeg, but my outputs look just like my input videos. If there is a difference, I certainly cannot see it.
However, the speed only holds if I use 60fps video or less. Making color changes, brightness, zoom all seem to be reasonable and on par to what I'm used to seeing in shotcut.
However, if my source material is over 60 FPS , the speed of encoding significantly drops off for something as simple as "trim".
Going forward, I can convert my sources in ffmpeg, no biggie. I'll have to keep my sources tho for future 'just in case'.
Attached is a photo of my settings that I'm using for OBS and cin with nvenc for going forward.