Adding music // meta data

I can only help you with the first question:

Go to
Settings - Server - Agents - Albums - last.fm
make sure that the line ‘Local Media Assets’ is at the topmost position
Repeat the same under
Settings - Server - Agents - Albums - Plex Music
+
Delete and then re-create your music library,
go to the ‘Advanced’ tab
enable ‘Use embedded metatags’


Here are some tips regarding music

multi-disc albums

handling singles and EP’s
https://forums.plex.tv/t/best-way-to-add-album-singles-ep-to-a-premium-music-library/128108/8

possible ‘side car’ files for music

soundtracks and ‘various artists’