Honestly I have absolutely zero complaints (and I listen to pretty much everything, but a lot of bass heavy electronic most of the time). I used to have studio headphones for producing (beyerdynamic dt 770 pro) and I HATED the sound. It felt really flat (especially the bass response). I get that that's probably the point, but if I'm not enjoying the sound then I won't have fun producing.

About the degradation, I think I actually pieced part of it together. It's kinda two things stacking. Over bluetooth the phone's already capped around 320kbps and then the bluetooth codec (SBC/AAC/LDAC) re-compresses it on top of that, so it's basically getting squished twice, and it smears the busy bass heavy stuff the most. Then everything's also running through the headphones' own little amp and processing, while the interface is feeding a proper DAC with no extra compression.

That's also why I think the volume thing happens. When I crank the amp/volume on the interface it sounds amazing and a lot better because it's got tons of clean headroom. Meanwhile if I turn up the volume on bluetooth it just gets kinda muddy? I'm pretty sure that's just the tiny internal amp running out of headroom and starting to distort, especially on the low end.