The buses back go the same way the buses there. They are Mears buses.
For MK there and back - drop off and pick up at TTC then back to Dolphin. They do share with Swan. It is not near the YC bus stop at MK. Since they are not Disney buses they can not pick up or drop off where the Disney buses do. They must do so where other charter and non Disney resort buses do.
For AK - they pick up and drop off in the same area the ride shares do. It might actually be a tad closer than the Disney buses.
There are no buses to Epcot or HS, you can either take the boat or walk.