I misunderstood. I thought the system would be running Plex Media Server and you wanted to take advantage of Hardware Accelerated Streaming.
Video transcoding, both decoding and encoding, occurs on the server. If you have a compatible CPU with internal GPU or discrete GPU, Plex will use it instead of the CPU for the video decode/encode process.
What will you be using as a client - PMP, Plex for Windows, something else?
If you’re using PMP or Plex/Win, you’ll need a video card that supports 4K output. Both of those will direct play 4K video, even when connected to a 1080p display (I have a 750 Ti card connected to a 1080p TV. PMP direct plays 4K HDR movies even though the 750 Ti does not support HEVC video).
However, if I remember correctly, neither PMP nor Plex/Win supports HDR video output. The video is tonemapped to SDR. There was a thread about this recently. I’ll see if I can find it.
Edit: See this thread. Plex Media Player does not passthrough HDR video to the attached display.
