have about 1tb of mp3 exclusively, much of my files are a pita for example:
many are not on discogs
many are vinyl or cassette rips labeled side A or side B
the rest is normal
For things that aren’t on MusicBrainz (the default data-source for beets’ autotagger) or Discogs (secondary source, can be enabled via plugin)… If your existing tags are good, you can disable auto-tagging entirely when importing them, either by passing the --noautotag command-line option ( -A for short, but do take note of the capital) or by setting autotag: no in the import: section of your config file. I believe it’ll then just accept your existing tags as authoritative, so make sure they’re correct and consistent first! Ideally, you could familiarize yourself with the MusicBrainz style guide, tag the things that aren’t yet in MB according to those guidelines, and then once you’ve imported them into beets it can automate the process of submitting those albums as new additions to MB so that others can benefit from your work.
I would expect the default handling (which merges multi-disc albums into a single entity with continuous track numbering straight through) to automatically merge side A and side B in the same way, though I haven’t tested this.
im unclear as to what method is best for folder hierarchy, open to suggestions! i used to like artist - album (year) but ive heard that will cause complications as the directory gets bigger…
This is very much a question of preference! Personally, I like my list in chronological order (and I want a 1995 remaster of a 1972 album to still register as 1972), so I use something like:
$albumartist_sort/$original_year - $album/$track $title
i also am trying to learn about clutter, is it possible to move all the clutter with the mp3s? many albums have alternate box art, pdf of the complete liner notes, etc…
As far as I know, beets doesn’t have that built in. Given the customizations you can make in the clutter: config option, it would be cool to have a mode (‘voracious’?) to apply your move/copy/link preference to “everything in the folder that doesn’t match the clutter list”, not just the music files themselves.
for singles, is it possible to just have a folder inside the album artist called _singles ? that might make the best sense? but again open to learn!
I’m pretty sure it’s possible, but I’m not sure it’s a good idea. One thing you can easily do is break your artist folder into subfolders for studio albums, singles, live recordings, etc, using the $albumtype variable in your Path template.
If you really want to pull apart your singles and throw all their tracks in one folder instead of treating a single as a type of release with its own folder… you could use the “singleton” functionality to do it. I think this is a bad idea, so I won’t include specific instructions for how to do it. 
If you want to get really clever with the Path notation, it is possible to have studio albums (default) go directly under the artist folder, but define specific rules for singles to go into a “Singles” subfolder in the artist folder. The Path notation is seriously powerful!
lastly. for compilations, how?! lol
Example lifted from the docs:
comp: Compilations/$album%aunique{}/$track $title
Modify as needed to suit your preference.
h*** of a program !! thx!!
If a release is marked as a ‘Compilation’ in MusicBrainz, it’ll appear in the Compilations folder in your collection.