I'm using Atlantis, and i can say if you want to use it via USB input, you should have a seperate computer for playback only. It's USB input is too picky. (My desktop cannot feed it properly, but a seperate entry grade laptop with empty task manager can feed it.) Or you can buy a usb isolator/reclocker; something like schiit wyrd and it should be fine.
I haven't tried optical input, but I've tried other three; USB is just fine compared to other known multibit dacs, Coax is better: with Coax input it gains slight body. But, for me, the best input is BNC. The body it gets via Coax is better/clearer (i dont know the terminology well) with BNC, mids gets slightly lushier.
But I have to say, the changes with input differences are less noticable then changes via tube rolling. In fact, if you dont have "the ear" and "experience" or mid-fi amp and headphone setup, you might not notice the differences between inputs.