Sorry for the late response guys
Thank you tjinc, your comment explains a lot. I always found it a bit odd how MusicBee does that since Artist and Album artist are not always the same,
"Album artist" is the "main artist" or the artist who the album belongs to, "Artist" on the other hand could be any artist or artists who contributed to a track or multiple tracks within a given album alongside the "Album Artist" or the main artist. at least this is the way I always understood it. when browsing the music files using the regular windows file explorer you'd actually find that "Artist" metadata field is called "Contributing Artists"
that's why there's confusion sometimes when using MusicBee. one example is when using the "Tracks" view where it shows the details of every track in columns, the "Album Artist" column would show the same value as the "Artist" column giving the impression that this value is populated in that track while in reality it is not and just mirrored from the "Artist" value
Other prominent example is when you're choosing between "Artist" and "Album Artist" for the Thumbnail browser:
If you choose "Artist" it lists every single artist that exists in the "Artist" field of all the tracks in your library, but for the tracks that don't have "Artist" populated, these are all grouped together under [Unknown] even if these tracks have "Album Artist" populated, that behavior makes some sense on first sight (since "Artist" is not populated for these tracks) while in reality it should utilize the "Album Artist" field and list the artists there as well,
If you choose "Album Artist" for the Thumbnail browser on the other hand it lists all the artists that exist in both "Album Artist" and "Artist" Fields, which doesn't make sense if you follow the same logic. tracks that only have "Artist" populated and no "Album Artist" should be grouped under [Unknown] as well, artists listed in that view are not always the album artist
I understand now that this behavior is due to MusicBee treating "Artist" as an "Album Artist" which doesn't make a lot of sense and causes confusion,
I think MusicBee should treat the "album artist" as an "artist" and not the other way around because "artist" is not always the "album artist" but the opposite is true
I realize that this is a small detail, but in my opinion it's quite important. in my use case for example, I set the Thumbnail browser to show "Album Artist" for easier browsing, it narrows things down a lot better than just "Artist", that way it's only showing my "main artists" or the artists I have albums for in my library (somewhat like browsing folders), a very clean look.
choosing "Artist" for the Thumbnail browser populates the panel with way more artists than I need or care to look at and it makes the whole thing very cluttered and not very pretty to look at (I'm sure that this view has it's use cases though). but in my case I'm just interested in listing the artists that I have albums for, that's why I'm suing the "Album Artist" view, but then whenever I add new tracks to my library that don't have "Album Artist" I have to manually deal with the stray "Artists" that pop up in there and clutter my view. as a workaround I create a custom "Album Artist" to group these tracks into
Ideally, I think MusicBee should treat "Artist" and "Album Artist" separately or just treat "Album Artist" as "Artist". I think this would eliminate all confusion and make the terms make more sense inside the app
That way the "Artist" view would list all the artists from all the metadata fields it could find artists in, and [Unknown] there would only have the tracks that don't have any artists in all the metadata fields,
and the "Album Artist" view would just list the album artists as the name suggests and [Unknown] there would only have the tracks that don't have an "Album Artist"
Sorry for the wall of text, but that's my two cents on the matter. I hope sharing my perspective would be useful in any way and help users eliminate any possible confusion when using the app.
Lastly I wanna say that MusicBee is a phenomenal app as it is, but it's just my perfectionist side getting the best of me and want to see a great app be even better.
TL;DR
That said, returning to the issue of templates, I personally think <Album Artist>\ should just populate Album Artist and <Artist>\ should just populate Artist,
but making <Album Artist>\ populate both like Steven suggested would also be fine and would make sense, since the "Album Artist" is also an "Artist"