For those who are about to install 2020+. I would suggest having about 3 feet of extra red wire, and possibly some of black wire if you want to ground somewhere else. Also Ring terminals if you want a clean look.

The extra red wire would be to extend the positive (green) cable from the switch to the relay and camera connections that would be located near the back of the radio. While you can mount the relay anywhere, it would probably be best behind the radio since there is room and its pretty hidden. The two harness already has extensions about 3 feet long to the switch. Without the red wire, you would have to finagle the relay further out if you want to mount the switch in one of the left hand spots.

The black wires are entirely optional to tie all of the grounds together. I used one on the side of radio, one near the switch and one in the bay for the grounding points.