I would like to know if there's a way in which every time I add a song or album into "My Music", it is saved in the device automatically, without selecting the option "Save for Offline".
I've written a short blog post explaining how to do this.
You create a smart playlist with a single rule which checks if the
iCloud Status equals
Apple Music. Check the
Make Available Offline setting for this playlist and all Apple Music songs/albums will be automatically downloaded when you add them to your library.