I have a bluesound. I think the streamers that have USB are higher $$. Your streamer and DAC will give you satisfying sound. I am using a COAX, this is what is most common.
for the new release bluesound node, the usb digital output that is coming will satisfy some users who like that connection interface
i have had very good results using spdif digital out from the node 2i... since late 2019 i tried and compared it to much pricier streamers from auralic, aurender, innuos, mytek, and using them as streamer only (not their dac outputs) with their suggested output connection, i did not hear a difference in sq
in theory, the spdif format slaves the downstream dac to the clock of the upstream streamer, whereas usb 2,0 will allow the dac to slave the server... but if the sending unit clock is sufficiently stable and does not introduce jitter (and the connection length does not create reflections), the bitstream can and will be properly received at the dac using spdif