The one in post 2 looks nice. I lucked out and got one recommended on RV.net a couple years ago which I can no longer find on eBay. It had lines inserted at the camera (or not, two video outputs). The lines are very helpful for distance perception and where the back end will be if I back up another few feet. A 7 inch display is nice; larger would cause serious problems for mounting on our C. I have the camera high up mounted just inside the back window looking down so I can just see a bit of
the spare wheel on the bumper. I find this much more useful than the view from the license plate. In fact the backing up camera is enormously helpful. You will love it. If you tow anything, be sure to wire it so you can look behind while on the highway.
Having used both, the wired one has no interference while the wireless one has some. I now have the smaller wireless one looking sideways on the driver’s side but it isn’t very useful. I have trouble interpreting what I’m seeing because it isn’t a view I’m experienced with like the rear view being like a mirror.