Usb or Optical

It probably doesn't matter at all.  You likely won't be able to tell the difference.  I have had optical connections that I thought were inferior but I didn't have any incentive to figure it out, I just switched to USB and was happy.  Most roon users, including me, use USB.  There is some anti-usb rhetoric out there.  I don't believe it but some do.  Either way, given the level of equipment in your system, you shouldn't be affected by it.   

Jerry

Both are decent, USB sounds and looks good to me. 

Maybe I'll try both I'll just buy two cables pop on my headphones and see if I can hear any noticeable difference.

That SMSL is rare streamer/dac with optical input, so optical solution really inexpensive for you. Whether usb or optical superior will have to be determined by you.

Thank you for your reply I'm going to try optical and USB and actually see if there is any difference.