Take a look at this chart - to identify someone with the 2.8mm lens that is popular, someone would have to be within 13 feet of the camera, but realistically within 10 feet after you dial it in to your settings.
As others have said, the varifocals are intended to be a set it and forget it and they are motorized and you can zoom in from the app or the computer, but as someone mentioned, since there is not pan or tilt, it is useless to try to zoom live as it zooms to the middle of the image.
Regarding a tighter field of view that would allow someone as you mentioned would then be able to come up to it and disable it, that is what redundant cameras are for. Always have one camera in view of another so if someone tries to disable, you still get them. Many here have 3 or more cameras just at their front door.
As others have said, the varifocals are intended to be a set it and forget it and they are motorized and you can zoom in from the app or the computer, but as someone mentioned, since there is not pan or tilt, it is useless to try to zoom live as it zooms to the middle of the image.
Regarding a tighter field of view that would allow someone as you mentioned would then be able to come up to it and disable it, that is what redundant cameras are for. Always have one camera in view of another so if someone tries to disable, you still get them. Many here have 3 or more cameras just at their front door.
Why I Like Redundant Views/Multiple Cam Views
A lot of newbies ask for help with their camera setups and most think that they can get by with a single cam to cover quite a bit of area. While that is possible if all you are interested in is a wide-angle overview, it usually will not give you a great chance of getting a face shot good enough...
ipcamtalk.com