Great. Someone to poke questions at
What TV do you have? Reports of Netflix/DV not working too well with LG TV's due to Netflix needing 60hz for 4k but LG TV's can only do DV at 30hz or something. Won't be an issue for me if this is restricted to (some) LG TV's.
Can you confirm that Netflix/Amazon Video is doing DV/HDR with proper colourspace and refresh rates for media? ie: Playback is not a judder fest.
Since you are using Plex I assume Kodi will run just fine but if you could take some time to install Kodi and confirm refresh rate switching, colourspace switching etc that would be fab