Concerning imported music, which is music that you select manually to be able to listen to offline:
You can change your quality preferences in your app settings by clicking on “Imports/Downloads” in your settings. This is accessible from the My Qobuz tab, by clicking on the cogwheel icon on mobile applications or by clicking on your profile icon in the top-right of your PC/Mac applications.
You can also select your desired quality when importing/downloading music
On iOS, you can also choose the quality of download for albums, tracks or playlists by pressing and holding the import icon either on the page or in the menu.
Cached music, the music that gets stored on your application while you listen, will be downloaded in the same quality in which listened to it
Please note: the maximum quality available for offline listening depends on your subscription plan and on the different qualities that are available.