regarding a 12v camera, i've seen references to 12v cameras that people are starting to use but you have to know if the camera will be happy with 3S power since that will nominally be 11.1 volts. if you're not sure and if you also don't know for sure that the 12V camera will give a much better picture or added features that you've not sure if you need then I'd just stick with the 5V camera, keep it simple, and use it until you really know for sure more about the 12V options.
Bart