BNC and USB from streamer to DAC

The thing I'd compare to though is optical.

While USB wins for reduced jitter (normally) I'm afraid even modern DAC's still may lack galvanic isolation, and introduce ground loops, which _may_ be heard as hum, or may evidence itself as jitter (as some tests have shown).

Usually yes, but I'm not sure how well the USB receiver will react. There's quite a bit of handshaking going on.  Try it. 

Erik