That was my thought about part of the process too, like does YT and Spotify use a lower bitrate if you're using usb out vs analog out vs bluetooth? Plus if the data connection is 4g vs 5g or sitting in the driveway using wifi, how does that affect the streaming?

I'm not an audiophile by any means, but streaming almost always sounds worse than CD or even sometimes radio.

Yeah - with bluetooth, definitely there's much, much lower quality in some cases. Initially when trying cars I always used Android and bluetooth, and it gave me very bad impression of some of their audio systems. Then when finally bringing a cable for Apple Car play and using my partner's iPhone, the sound was totally different.

But it does also seem to depend on a car. Because I'm pretty sure I've had some very good experiences with bluetooth as well. And a case where bluetooth Youtube Music sounded good, and bluetooth Spotify sounded bad.

In addition both of these apps have different volume levels despite car having the same volume level, and Android has different volume levels compared to iOS, so all of it combined, testing around made for an annoying experience.

Audio doesn't use very much data. CD bitrate is 1.4Mbps while USB2 is 480Mbps. It would have to super bad to for audio to have problems, and USB2 is super reliable.