You want both wired. Not a big deal and I really like the extra functionality.
B+ goes to the battery.
Acc goes to power that turns on with the ignition.
This way the screen turns off when you turn off the key but the bump sensor will record with the screen off if someone hits your car when parked. Great function!
I extended the wires and pulled them all the way to the fuse box under the rear seat where I found 2 great wires, one that was always powered on and one that went on with the ignition.
On the rear camera you have a red wire, if you connect that wire to your reverse lights then the mirror will change the camera angle so it points more down when you reverse. Totally worth doing.
wolfbox.com