Thanks mate, I tried that, but it seemed fall back to the handbrake Cli option no matter how I twisted the syntax. I read a ton on the, as you say terse, documentation, so true btw!, and found a ton of info concerning the options for the h264_nvenc encoder that appeared to be different than those of the HEVC one in the current version(s) of ffmpeg
I can post a copy some test profiles tomorrow when I get a chance if you are up for helping with some troubleshooting to get the profile to work. At the moment I am relying on alterations of the builtin h264 profiles based on the libx264 encoder which certainly can utilize the HW acceleration, but I would like to build one purely built on the HW encoder a la the one you made for HEVC