Roon settings with Oppo 4k player

I make connection with my Oppo 4K player in my network. The player is connected with his digital out (coax) to my Amp and now I have sound. BUT how do i get the best possible sound out of this combination. What are the best settings for volume etc in the set up of the Roon settings? The problem is that my Imac is 10 meters away from my Hegel amp and I can not put it somewhere else. Because of this a usb does not work because the distance of 10 meters is to long (I tried !!). So if I want to use roon I have to do it the Oppo 4k way. Do you prefer this route or is streaming with upnp a better option to get the highest quality audio?

Best Fonz