Yo,
I have an iPhone 4 and a 2015 fit LX. The sound quality is best if music is played via USB/iPod setting vs. bluetooth. In order for your bluetooth music i.e. (pandora, spotify) to be visible on your "iPod setting" screen there needs to be at least one song saved on your iPhone (it could be a podcast as well). If not, the screen will just read "no song". It doesn't matter what the song is, but it needs to be present for song info to appear from other software (spotify, pandora). It took me a while to figure this out.

 

Bluetooth is limited to 328kbit/s so it is compressing your audio to stream it, that's why the USB connection sounds better.