From a brief perusal of my library, audiobooks purchased from the iTMS are protected AAC files (m4p). Even after iTMS ditched DRM for most tracks, some exceptions included the "free track of the week," discovery download, and freebies from Starbucks, I think. I know the "free track of the week" and "discovery download" were. Unless you intentionally delete and then re-download the track, I think it stays in the protected version.
As for Apple Music tracks, it's a little more difficult for me to say. I keep most of those online, and those were skipped. I had 74 out of 100,714 that were reported as "protected." That's the best I've been able to track down.
My MC25 library now shows 90019 files.
I know MC imported Podcasts still listed in the iTunes XML file, even when the "location" is an URL and not a file on the local file system.
It did import all the Music playlists, which is decidedly unhelpful (most of them have 1-2 tracks).
The import also took freakin' forever, and there was no indication what was happening or how long it might take. The CPU usage for MC25 shot up and stayed that way for a number of hours. I eventually gave up on it and went to bed, so I'm not sure how long exactly it took.