Most of my videos are working correctly with HW to HW, but I have some videos that are failing to hw decode, so it does SW to HW.
If you have specific examples, you should shutdown/restart plex, playback and reproduce the video that fails to HW decode, then download logs and post them here or a dedicated thread with ALL your detailed info on your server/client (specific plex versions, what cpu/gpu/ram/etc).
Dev may also want a sample of the file which fails to hw decode.
https://support.plex.tv/articles/201035968-generating-sample-files-from-media/
it seems in my situation, most of the ones failing to decode seem to be older 720p x264 rips.
see @ PMS 1.17.0 - Not hardware decoding some h.264 media with Nvidia GPU on Linux
