@ohneSchatten, I must be a bit dense as well - because like you, I still am not 100% sure what happens (or doesn't happen) once I cancel my iTM subscription as a current AM user. I wish I'd seen your post earlier, as I just opened a thread containing pretty much the same questions here:
Questions about canceling iTunes Match (Apple Music user)
I'd love to know if you did experience any issues after November 5 and if your library was affected in any way. I'm mainly worried that something might get screwed up (I have invested an enormous amount of time into adding custom artwork, lyrics and metadata to my files over the last decade) and the thing I read about the different catalogues for AM and iTM confuses me as well. I understand that all the tracks that were matched, subsequently deleted and then re-downloaded as DRM free AAC versions should remain unchanged and I guess the same is true for my uploaded CD rips. Can you still access all your tracks on all your devices just like before? Did you notice any differences regarding your music files / iCloud Status / artwork / metadata / etc. in your iTunes library?
I agree that Apple could have done a better job at explaining in clear language what's going to happen if long time iTM users cancel their sub. I've read a bunch of articles about the subject but none of them clearly stated "this is what's happening to your library when you cancel iTM." So now I hope you can tell me, so that I can make an informed decision 😉 Thanks in advance!