Installing Rearview Camera Question

That's what I did and it ended up being easier than I thought it would. In my Class C I used a coax cable and a 4 conductor sheathed cable so I only had 2 physical cables.

I just ran them through the floor pan of the cab near the firewall and pretty much followed the inside of the "C" channel frame all the way to the back. I zip-tied it to an existing wire harness at each fastener location and the hardest part was threading 50' of wire over and under different things that were in the way.

It's really well protected under there and much easier than trying to run it inside.

I did so by staying inside the frame rail & using wire loom. Just run the wire inside of the loom first, then string it along the rail.

So long as it's appropriately anchored, reasonably routed, and protected from the elements (with waterproof connectors for any joints, etc.), it should be just fine. Might be best to use a sturdier/thicker cable than would be minimally required going via the interior just for physical protection, or running it in some sort of a tube or bundle if it seems fragile.

I'd probably avoid going on top of the roof unprotected unless I knew the wire was UV rated. There's no real concerns about electrical safety for a video cable, as the voltages and currents involved are miniscule, so pretty much the worse that can happen is that the rear view camera system goes on the fritz.