I recommend a HARDWIRED system for mounting on the rear of your camper. The wireless signal has too far to go and a lot of potential for interference going from the back of the trailer to the front of the truck.
For the truck, you have a lot more options. You can see if your make/model has an option for a factory system. My Tundra didn't have the factory system, but I bought a Rostra aftermarket system that connected to my prewired truck. Worked great.
My Ram had the factory system, works great.
A quality wireless system with its own dedicated screen is a simple, inexpensive option that will work well for the truck, with minimal distance and interference between camera and monitor.
Another option is something like the iBall system. That is a temporary magnetic mount camera system, not meant to be left on the truck full time.
Lots of options, good luck!
2015 Ram CTD
2015 Jayco 29QBS