I may be mistaken, but I believe the smaller boats don't accept passengers using manual wheelchairs. There's simply nowhere to put even a folded chair.
No ramp is used on these, unlike the Epcot Friendships. The pilot brings the boat close to the dock's edge, and people run chairs, ECVs and large strollers over any gap, which is usually minimal. If the boat deck isn't pretty level with the dock, a crew member asks passengers to move to one side of the boat or the other to raise or lower as needed.
Yes, this is how it usually works. If you get to the dock before the boat arrives, the skipper will know which is coming.