actual fitting of rear dash cam

Hi I know there's a lot about this but I can't find any advice as to where to fit the camera and does it have to connect to the reversing light +ive or could it connect to the high brake light positive?
Also what is the best way to run the cable? If connected to the rear high brake light it's fairly easy but if to the reversing light then I'm stumped.

A lot of questions but any help gratefully received.

Vehicle is 2015 outlander PHEV plug in

Not sure what you're trying to achieve? Why do you want to use either the reversing or brake light feeds? Surely the camera would only come live when either reversing or braking? Or am I missing something?
You can fiddle a feed through the flexible trunking at the top of the tailgate with a bit of time, so I used a feed from the front, up the door pillar, and under the edge of the headlining.