You're right, so far its a mess. An example I have:
Alabama Shakes had a free single when their most recent album came out. I legit "purchased" that song for free and added it to my iTunes Match collection. Now, with the free trial of Apple Music. I have to remove this item from my library to be able to add the whole album the single is found on to my Apple Music library (ie. it's not smart enough to see that I only have one track, not all 12 tracks in my library).
The thing is, if I remove the iTunes Match version from my collection, next time I sync my Nano or classic guess what? That file will be removed from those devices as I've now moved the file from iTunes Match to Apple Music and Apple Music doesn't support iPods.