If you’re driving 400 miles you may opt to listen to music and that portion is on the screen and you would hear in 1 mile take exit 39a and stay in right 2 lanes…. You can select other apps (such as music) and the other app displays on the screen and you still have the turn by turn running at the same time. If you select your phones map app you have to choose it to be displayed on screen. This allows me to hear the turn by turn better.
What I do when I am unfamiliar with an area is start my music app and pause it. On occasion the sound from both can “conflict” which each other and the map nav is hard to hear. If I am somewhat familiar with an area I’ll leave music in the back ground on. Yes turn by turn come through the cars speakers.
I don’t have Subaru navigation but use navigation through apple car play.