There is no apparent advantage in using USB because it's a PCM only DAC.
You will be able to play DSD as DOP using the N20s settings but not native DSD.
Upsampling via the N20 is available for AES/EBU and COAX outputs.
I use a Musetec 005 standalone DAC with my N20, I highly recommend it, you will then be able to play native DSD via USB.