Tidal - Poor sound quality


I just receive the e30 dac and

  1. I like the sound that gives over USB connection to my rpi4.
  2. I have conencted the optical input to chromecast audio and at the same external amplifier volume the volume from chromecast is higher the the one from USB volumio and it appear to me to be more clear or it is just and impression? I listen qobuz.
  3. My brother has a CCA audio conected directly via analog to amplifier. Does it make sense to buy a e30 to conected via optical? He listen spotify.
    Thanks for your support.