first, netflix 4k and plex are entirely NOT related.
second, if you are trying to play full 4k bluray rips, then your problem is most likely you do not have your stick plugged into an atmos receiver, your tv doesn’t support the HD audio that is included in such rips. select a different audio stream (ie 5.1 or stereo)
third, if you have subtitles enabled, they can cause problems and transcoding if the subtitles aren’t compatible with your device. disable subtitles on the plex client app settings.
forth, if your tv isn’t 4k (you didn’t specify), then plex will transcode and downscale it to 1080 or less regardless of any of the above.
finally, please read @ Plex, 4k, transcoding, and you - aka the rules of 4k - a FAQ
all of your questions should be answered somewhere in the thread.
