Thinking about adding a 2nd AC

Is the second AC normally ducted or is it normally one of those direct vent or whatever they call it when it dumps into the room it is set up for?

Ours, in the bedroom, was added later and it is direct output into the bedroom. I think that would be true of most added units, though there may be some trailers which allow adding into the existing ducts.

Unless I am wrong, most added ACs are direct output.

BTW, we have not found this to be a problem. We use both ACs when we arrive at campsite, especially in the Texas heat and humidity, but have never had to run both after the trailer cooled down. I expect there might be some really hot days when it would take both units, but we have so far avoided staying in such conditions.

Sometimes we run the bedroom AC and turn off the main unit when we are sitting in the living room and watching television. That works good. It would work even better with a small fan to move the air out of the bedroom, but we always forget to bring one.