You need your phone as it provides the music to the fit2. The fit2 is a wonderful exercise tool albeit it needs a phone for music playback.

If you want to have only your watch then consider the LTE versions of the GW GW3 GWA GWA2 that you’ll need to add a cellular plan on and then can use Spotify premium without the phone.

You can get the non LTE versions of those but would need to transfer downloaded music to the watch itself but that’s not Spotify, I mean like actual music downloads.

Also an annoying thing about the fit2 is that when you’re on an active exercise programme you can’t change tracks using the watch without ending your exercise program so you have to use your device