What GM should have done is eliminate the 4 pin connector in the bed and installed the camera ports there also. If you can have two 7 pin connectors you surely can have two camera ports. Most of us have a 7-4 pin adapter plug to solve that problem.
Solves the problem for 5th wheel and bumper pull also.
You will probably get more than 30 opinions. This kind of thread brings out the worst in people. For what its worth, I use Shell Rotella T6 in my truck, tractor and motorcycle.
Looking at the wiring schematic it looks like switch 5 is dedicated to the roof beacon. The others are user configurable. Attached are the installation instructions.
Joe
UI Bulletin 153_wip.pdf
I have an upfitter kit that came with new 2020 Silverado 2500HD truck. I would be willing to part with it as I don't ever plan on putting a plow on it.
Joe