As noted the plex web app doesn’t direct play hevc, other than on safari.
The dash board @ https://app.plex.tv/desktop# - settings - dashboard will show you if something is being transcoded, and whether it’s a local or remote stream.
That remote limit doesn’t apply to local streaming.
For more 4K info check @ [INFO] Plex, 4k, transcoding, and you - aka the rules of 4k
