The music folder is not a problem. I have my main PC, where I continually add songs to my music folder, which MB monitors. Every new song I add then gets allocated to a playlist, which MB also monitors, no problem. I do a sync to second PC, (or you could copy), and MB on second PC is identical to main PC. Copied my music folder to sd card on tablet, works in MB, but it doesn't matter if I copy the MB playlists to sd card or on to MB folder on C drive, playlists are incomplete, not locating path to many files. That's when I discovered the files in MB playlists spread over two different directories.
I have to work out the correct way to add files to the playlists in PC 1 so they show up on tablet, then rectify playlists on PC1 so that playlist sync will work accurately to tablet. I can't understand why the playlists files are spread over two directories in PC1, I think that's the first thing I have to resolve.
I think either way, I will have to change directories to the existing unlinked playlist files on the tablet, via PC1, so that they will play on tablet after sync.
So basically, I'm after the same result as you, but somewhere my playlists files have been mixed up.