I think one overview camera would be ideal. I didn’t know about the masking whil recording thank you. I’m going to watch for a computer on eBay and order up the one varifocal for the time being.Don't try and buy the whole system at one time. Get that 5442 varifocal and use a test rig as described in the Cliff Notes to test specific placements. Do not run wires or mount the cam until you have tested the exact position, day and night, with a person walking around in the cam view.
Put some LED bulbs in your driveway and front porch lights and keep them on all night, use a timer. I use 5000k temperature 500 lumens bulb in the coach lights and 5000k 1750 lumens in the pot lights on my porch. Even if you can't get good enough lighting for color at night, the visible light will help with the IR picture.
If you have that view on your fence that you would really like to have, realize that you can mask the video. See my still below. I did not want my cam pointing into my back neighbor's pool. You would not see much, but it just seems creepy to me to record that.
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@wittaj has given you some good info on sensor size. Here is a little more. It is not that a 4MP cam is 'better' than an 4K cam per se. Low light performance is based on how much light gets to each pixel. So if a cam has a 1/1.8" sensor (0.555 inches), each pixel would get much more light to it if there were only 4MP spread across it than 8MP from a 4K cam. Of course other things are at play here, like shutter speed, aperture setting, and the lens used. But most 4K cams in the prosumer lines are on 1/2.8" (0.357 inches) or smaller sensors. So that 4K cam on one of those sensors will get even less light per pixel than the 4MP on 1/1.8" sensor. The wider the aperture, the more light gets in but the depth of field is less so focus becomes an issue. To get more light to the sensor, the shutter can be slowed down, but that will impart motion blur. You can up the gain, but that imparts noise. It is no different than sports photography. There are trade offs that need to be made. So getting a big sensor and less pixels is the easiest way to maximize the light to each pixel without imparting negative issues.
There is nothing wrong with having a wide angle cam, one that we call an overview cam, provided that you realize it is just that, an overview cam. It will not give you any facial info but can supply other data like clothing color, markings and logos, vehicle info, perp direction of travel, etc.
Thanks for all the great info everyone.