Some DACs work better with ASIO async, some with the optical s/pdif connection.
I had a NAD C390DD for a while, and from memory I thought that was better using the USB connection. I can't hear the difference between a 24/96 and 24/192 (or CDA to be honest), so that was never a consideration for me. The dacmagic plus was much better using USB. The Chord Qute I tried out for a couple of weeks was the same whichever connection I used.