BNC and USB from streamer to DAC

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

Asynchronous USB delivers just data - you cannot make it any better.  The only disadvantage  in comparison to S/Pdif is the amount of electrical noise injected into DAC, that can affect the sound.  When you have both cables connected USB should win.

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).