Apple Music "New Music" "Chill Mix" playlist question

[swandy]

I just added the three Apple curated music lists to my library (New Music, Chill, Favorites) and downloaded them to my iPhone. I would also like to add them to my Apple Watches.
The question is what happens when each week the list is changed? Are the downloads on the iPhone and Watch replaced by the new songs or are those songs kept on the various devices? It is more of a concern for my Apple Watches because there is no way to delete all the music on the watch, just by removing playlists and re-syncing.
Any info/experiences would be appreciated. Thanks.

 

[Tartarus]

As far as I know the songs get replaced by new ones every week.

This also applies to the Watch. You won’t have to worry about running out of storage.