Sorry, I don't have the terms in english. Option are in preference / qualité sonore in the iOS app.
If you know the difference (and the name in english), I thank you to learn me 🙂
"qualité du streaming" is the streaming quality. It is the quality used when playing music that is not on your phone.
"synchroniser la qualité" is the sync quality. It is the quality used when downloading a song to your phone to play offline.