Interesting, but I’d have to say that I’ve been contempt just using an app that doesn’t suck (musicolet). The comments about battery could hold a point to me if I were going on a week long trip, or something of the like, but anywhere that would happen for me is somewhere that I wouldn’t be taking music/phone for distractions anyway.
I think the finer point I agree with is being able to just have a copy of your own music and play it without being belt-fed opinions or ads. Managing it is always a bit of a pain, but I’ve got a system that works for me, and MTP on android works better than trying to deal with iTunes in my books.
Pretty much the same setup. I don’t really use playlists often though, and currently using syncthing to a NAS.