a few thoughts.
first, the AD-20 doesn't provide any sort of power for any type of microphone. so I'm not sure what you are using to power your mics, maybe you just left that out of your description.
and as far as clipping.
when running digital in to the MT (or any other deck that accepts a digital input, for that matter), yes, you are bypassing any analog circuitry in the deck, so you don't have to worry about overloading the analog signal path of the deck. BUT, 0dB is still 0dB. digital clipping is still digital clipping. none of that changes. with the AD-20 > MT rig, because the AD-20 doesn't have any level meters of its own, you need to watch the meters on the MT and adjust the AD-20 accordingly (so you don't clip).