So I can confirm that you are incorrect.
Having installed Python 3.11 fully, and changing the PATH variables, Plex breaks and no longer plays video (since the mpv dll is trying to do something it cannot, Plex just crashes) This is because the mpv64 plugin is no longer where it looks for python and the plugin files, since it then looks at the python folder...
When I copy the contents of the mpv64 folder into the python folder, Plex works properly again. And then I have the full use of python and its plugins... To which now function as to be expected. (I'm not going to waste time trying to identify exactly which files are needed in that folder since that's a huge waste of my time. But it does in fact work to run SVP and mpv64 from the python folder)
In this case it was the folder located in appdata/roaming/python/python311
PATH is now set to that location for python. And the contents of the mpv64 folder are now in that folder to accommodate compatibility.