I am using the thin RCA cables that came with it. The Node can also do optical, coax, and usb.
My Parasound Hint 6 has a built in dac of its own. It’s being bypassed by the Node dac via RCA.
Have you found better sound quality using one output over another?
My Node is my DAC so I use the line level outputs (RCA) straight into the amp.
If you are using the Node 2i as your streaming source then either Coax or Toslink would be the way to go, I would expect them to sound the same. The Node doesn’t have a USB output so that isn’t an option. The USB type-A on the back is for external storage devices holding MP3 FLAC etc., not audio signals.