hello, if you do not expect any 4k/hevc content to require transcoding, then all you need for cpu is about 2000 passmarks per transcode, according to the plex recommendations.
generally you do not need a gpu or hardware transcoding for 1080/x264 content.
4k/hevc is an entirely different story, as it requires upwards of 17000 cpu passmarks per transcode. In which case gpu transcoding offloads from the cpu to the gpu.
this chart will tell you want nvidia cards support what codecs Video Encode and Decode GPU Support Matrix | NVIDIA Developer
this page nVidia Hardware Transcoding Calculator for Plex Estimates will show you a range of gpus and approximate number of simultaneous transcodes they can handle.
this thread Plex, 4k, transcoding, and you will tell you all about 4k, transcoding, and how/why to avoid it.
one last thing, the most important thing for nvidia gpu transcoding on linux, is the amount of video ram.
a 4k to 1080 transcode uses about ~1.4 gig of video ram.
a 1080 transcode uses only a few hundred megs.
you can do your own math according to the card you choose.
