We stayed in 8588 on the Fantasy and had a fold down bench in the shower. We've also booked 8588 on the Dream for an upcoming cruise. I believe the room configurations are the same, and are the same as 8184 as both are accessible rooms. The photos you saw for 8184 may have had the bench folded up. In 8588, the bench was on the wall the bathroom shared with the room. I have a nice Google Cardboard panorama of the room, but didn't think to take photos of the bathroom. 8588 has an automatic door opener. It also closes on it's own and is quite heavy. Have the steward show you the override switch that allows you to keep the door open for a few minutes.
Guest service may be able to tell you what type of bench is in the shower and what type of shower stool is available.
You are going to love the extra space in the room. We have an ECV and were able to drive it into the room and turn it around to park it along the wall for charging. The veranda is a bit larger too.