There is another piece you are not showing. It is a holder for the DDS film holder. I can't remember whether it fits on the Super 23 or only the Universal. The Universal is a much more versatile camera, and the options on the Super 23 are far more limited in terms of accessories than the Universal. In fact for me, the Super 23 is deal breaker, once you know all the options for the Universal. The only thing the Super 23 offers is the bellows like perspective control for the lens that expands and contracts.
I know the box like back you need for the cut film holders. It's an accessory. Usually an expensive one.
Do you know if you can still get any film in 2X3, or do you have to cut your own???
That's the current large question that comes to my mind.
I love Mamiya press camera's but they can be a deep money pit when you go looking for all the bits and pieces.
The best Mamiya Press in my book is a nice clean Universal, with a 6X9 Type III roll film holder, and the 75mm type P lens that was made for Polaroid and mounted in a Mamiya Press Seiko shutter. Stop there.