I’m not aware of a direct nvidia vs intel transcoding chart, but you can find what nvidia gpu supports what codecs @ Video Encode and Decode GPU Support Matrix | NVIDIA Developer
see also @ nVidia Hardware Transcoding Calculator for Plex Estimates
for 4k you need a minimum of intel 7000 series with an igpu of 600 series.
nvidia cards you generally need a 10 series or newer (some older cards may have limited 4k support).
assuming a supported gpu, video ram is the most important thing for linux/plex transcoding
4k transcoding uses ~1.3 gigs of video ram per transcode
may also be useful @ Plex, 4k, transcoding, and you
