Apple Music / iCloud Music Management : Issue as a music Producer/musician using music to listen to original music while trying to also listen to iCloud library

So, I am a musician/producer/DJ (and an Apple user since 1989!). I am constantly revising music, checking mixdowns, listening to unreleased music, and promos of unreleased music, etc, while also trying to migrate from years on Spotify because I can't stand their business practices.

I've finally got my Spotify playlists migrated over to Music today, and switched over to iCloud Music Library, however, it seems that unless songs are in my iCloud Music Library, I'm unable to add new songs to playlists and manage putting them on my phone? I'm kind of confused about this process.

I've noticed a lot of my original unreleased music seemed to upload to the iCloud Libarary somehow, tho? However, working with high quality lossless waves and aifs, it seems the recordings of my live performance shows, or friends DJ sets aren't transferring (I also master DJ sets for friends). I need to be able to easily access these from my phone to check on various speaker pairings, and also for pleasure, while also being able to access my playlists I migrated from Spotify, so I can continue to find new music and refine my selections.

PLEASE ADVISE!!!! I'm dying over here. I really want to get away from Spotify. It never used to be this difficult.