I download albums in Apple Music and delete them once I’ve listened to them (like completely remove from library, so it says “Get” again rather than the cloud). Do these still count toward the 100k limit, or is the limit a total allowed at once?

There are no download limits for Apple Music. You can download as much as you want while you are subscribed.

The 100,000 track limit applies only to songs uploaded (not downloaded) from your local iTunes library to the iCloud Music library that were not able to be matched to a track in the iTunes Store catalog.

45rpm86 wrote:

So literally, as long as there’s room on my phone, I’ll be able to download/delete albums as much as I want?

Yes, that is correct.