Firstly I am still rather new to iPhones. I have an iPhone 14 pro with the newest release version of iOS and use maps for navigation and Spotify for music over Bluetooth in my wife’s car. The onboard navigation lowers the music before giving a prompt, however with maps the volume of the music is most times louder than the directions.
Currently i have apple music uninstalled because i only have the theme to 2001 on it and my wife’s car kept opening it instead of Spotify when it connected to Bluetooth. When iOS 17 releases i may revisit apple music.