Installed a Furrion 3 camera system on my 21 beginning of September. It was installed by a friend in a couple of hours.
There is a backup camera and side cameras where the front side marker lights are. The system was already matched with the 7 inch display. I really enjoy the rear view while driving, though on a really sunny day the camera closes down to avoid burnout and with sunglasses on it becomes extremely hard to see anything. The side cameras are great for checking lane changes but it can be hard to do so as the the selection is on the touch screen monitor and to have all three on at once makes for a very small rear view and squished side view cameras, your ability to see things may differ from mine. As the saying goes here on the forum YMMV.
Peace and safe journeys,