mdf: For the wiring on the dome cameras at least, the cameras allow either connecting from behind the soffit/wall wherever it is mounted, and from the side. I didn't have access immediately behind any of my cameras and ended up side mounting. I got a waterproof junction box from an electrical wholesaler and stuck all the connections in there and then ran ethernet along the face of the house to where it needed to go.
Connecting from behind is a royal pain if you've only got the ability to feed a PoE cable to it because they typically come with Ethernet, a 12V barrel jack connector, optional audio and trigger cables, and who knows what else. The way to deal with this is to mount it on a camera junction box and coil the various cables up inside it. Even then it's a very tight fit, I ended up with a 90 degree bend between the Cat6 and the RJ45 where it was crimped onto the cable to get it to fit:

If you're running cable to an external junction box, get some extruded aluminium rail and use acrylic sealant to attach it over the top of the cable run, then paint over it. Both makes it cleaner visually and makes the cable resistant to damage and insects building nests in/around it.


