I use beets for tagging, and it has no trouble with OSTs. It sets a different tag for Album artist and Track artist, and cmus uses the Album artist. Most soundtracks of the type you mention are under <Various Artists>.
I'm different from most people in that nearly all of my music collection is complete albums, so if that's not the case, then I could see how a file/folder layout would work better, and the artist/album view is more full-featured than the file-browser view.
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Also as far as I can tell, there's no way to filter based off of path (only filename) which might also be a good way if you prefer directory based organization.
