Before I even start let me say that I know the suggestion is to put 4k into it own library...
99% of my movies are 1080p and that is my preference for space and quality balance. However, there are a few choice movies that I'll want a 4k version of. I would rather my users get defaulted to the highest non-4k version but then have the option to select a different version if they were savy enough to do that.
Feels like it shouldn't be a terribly complicated feature. Have a "include x quality in default version selection". Or hell for my random case use if I could just manually reorder them I'd be happy.
I put the versions of movies in a folder by title, then add a suffix like " - HD" and " - UHD4K" to the move file names. It defaults to the first in the list which is in alphabetical order, and shows a choice for each version.
What has worked for me is to add the 4k version of the movie to my library. Then use the Plex Optimize process to pre-transcode a 1080p version. Then the user can select the … menu and they will see “play version” It seems some clients will surface the “pick version” menu anytime they click play but some won’t. Whenever I get a new 4k movie I optimize it until remote people have watched it and the I usually get rid of the optimized version. I also do it when I download a copy of the movie for offline playback (which believe it or not does work successfully….sometimes. But better than the never it was for a long time)
if you have multiple versions of a film (1080, 4K) when playing, your client should present a picker. if you can’t trust your users to choose the version you wish them to, put one into a library only available to them and the other into a library only available to you.
I wish the choices were more granular, but, currently, they’e not.
I think the only way to do this is as a client setting.
For example, I have this on iOS but other plex players have this as well.
However, I’m not sure if this will force a transcode or not
this doesn’t affect version access, this will merely determine whether the version they access with be transcoded or not, which opens up a whole other can of worms.