USB DAC digital output as digital input for Uniti-like products?

So what happens when the USB DAC (a-la Meridian Explorer) digital optical output is plugged into something like a Uniti streamer? Is it

(a) an intelligent system that leaves the data 'unchanged' or minimally processed, whilst transiting it's own (Uniti's onboard) DAC, or

(b) processes it the way it processes any digital input, i.e. akin to a digital music file from a NAS, is there such a thing as over-processing?

skipper.