I’m afraid this won’t work with Plex. (at least not satisfactorily)
Plex is very much album-centered. So even if you have a mixed bunch of tracks, they still need to belong to an album. (And no: a “mega-album” with several thousand tracks which holds all “Various Artists”-tracks won’t do.)
Plex always want this folder hierarchy: https://support.plex.tv/articles/200265296-adding-music-media-from-folders/
That applies just the same to Various Artists albums (i.e. “samplers”) .
If you files are well-tagged, it is possible to read their embedded “Album Artist” and “Album Title” tags and automatically move the files into the right folder structure.
Software like mp3tag makes this almost trivial.
What is also very important: if you store an album inside the “Various Artists” folder, its “Album Artist” metatags must contain only “Various Artists” and not something else.
If you have albums with other Album Artists, they must go inside their own “[Artist Name]”-folders.
