Bluetooth vs spark

[ogs]

Bluetooth is a lossy protocol, so yes Spark is better as it streams lossless to the Phantom. I do not know the quality of your Deezer stream so it's not straight forward to answer what is best in your setting. Usability is also an important part of it.
This thread over at the Roon community discusses your second question (among other things) https://community.roonlabs.com/t/how-do-...t-airplay/