I think those ought to be fine, I agree with stioc that if what's on there is new anyway, it's not worth switching to a smaller diameter rim only to air down a little more. The 16s will perform better when aired down, yes, but I think the exact difference wouldn't be too noticeable, as you can still air down the 17s. I'd mainly be worried about scratching those pretty rims on the rock more than actual performance.
Tires-wise, I've noticed by far a majority of people running Moab have ATs. Typically, they seem to have stickier traction on solid rock than their MT equivalents. Mainly, the drone from the MTs would get old over that mileage. My Toyos got pretty loud near the end, and it definitely is a source of fatigue you might not expect when driving long distances.