yes you can listen to music while navigating.
it seems there is no difference in performance.

i just called myself while listening to music and navigating - music gets paused and the phone-app opens

i declined the call, and the music would continue playing and navigation would continue.as well.

does anyone know how the call-function of the favorites work?
i added a friend to the favorites, but when i planned a route to his home, the menu didnt gave me the option to call him. the "call"-button was grey and i couldnt click it.
the name i entered is identical to the name i entered in contacts.