Disney reps have been saying 8 passengers, while Dopplmayr has been saying 10; my guess is that that is the difference between the typical-sized American and the typical-sized Swiss. I do not know if they will also allow standing; I would think that the answer would normally be no.
The open floor space between the benches has been described as the size of a standard shipping pallet, which should be adequate for a double stroller or
ECV to be parked there. They probably will not ask that strollers be folded, because the system depends on being able to quickly load/unload from the cabins without having to stop them (though I think with ECV's they will have to)