When I noticed the Artwork thing (Compilations Particularly a Mess, different art for most songs on every album) I immediately turned of "Show Apple Music", I never had "iCloud Music Library" turned on.
I went to iTunes, made a copy of the iTunes Library file in the iTunes music folder. Synced device, where I noticed that smart playlists had shrunk, 168 down to 140 etc. This was because all of my rated (Starred) music I'd purchased on the iTunes Store had somehow been put down to 1 star. 4 stars to 1, 3 to 1 etc. Anyone else have this?
Play counts were fine. Artwork was fine, and synced back to phone.
I disconnected iPhone, deleted iTunes Library File. Dragged back up in from earlier. Re-Synced. Seems Okay now.
Only thing is, some Smart Playlists are Duplicated on iPhone now. Some with artwork in Box beside playlist name in list view, some without.
Maybe updating to iTunes 12.2 will fix, maybe it won't...
Think I'll wait...
I love the up next feature on in the Music App though.
Hope this helps.