Come up with a cam plan and write it down. It does not have to be complicated or extensive. Just things like what specifically you want to be able to see, areas to be covered, cost willing to spend, etc.
Get one varifocal cam, like a 5442 and set it on a test rig as described in the
WIKI (see mine below). Test your ideas with this cam in both daylight and nighttime. WALK through the field of view and see how well your face can be seen. Do this BEFORE you run cable and mount cams.