Organize by composer, not composer and performers?

I’m starting to use beets to tag and organize my music library (still at the stage where I’m working out whether it suits my purposes), and I’m running up against a few issues.

The first is that when I import a classical album, a folder is created that is titled ‘$composer; $artists’, which makes it very difficult to keep recordings of the same composer (and particularly of the same pieces) in the same place.

So, for example, beets seems to importthe disk at (Bernstein’s recording of Mahler 4 with the Concertgebouworkest) into a subfolder called ‘Symphonie No 4’ of a folder with the rather unwieldy name of ‘Gustav Mahler; Royal Concertgebouw Orchestra, Leonard Bernstein, Helmut Wittek’. And it records Gustav Mahler as both Composer (where I want his name) and Artist (where I don’t).

I’m optimistic that this can be fixed (although perhaps not consistently for a library that includes more than classical music): can anyone help me find the right configuration that will help me do the following?

Firstly, create a ‘composer’ folder (so ‘Gustav Mahler’), and then to create an appropriately named subfolder within it (so something like ‘Symphonie No 4 - Royal Concertgebouw Orchestra, Leonard Bernstein’) within it?

And secondly, get Royal Concertgebouw Orchestra, Leonard Bernstein, Helmut Wittek (rather than Gustav Mahler) into the Artist tags?