170 degrees is a bit wide, but it is flyable. FOV is Field Of View.
You
really don't want to go too narrow, because then you can't tell what you are actually looking at, the middle of this tree or the middle of that tree.
You buy a security camera lens by it's "focal length". FPVer's usually use between 1.78mm (wide angle) and 4.0mm (narrow angle) focal length. The only reason I include 4.0mm is that I have a night lens that is 4.0mm. The next step beyond 4.0mm is 6.0mm and you really don't want to use that. Many cheap security cameras come with 3.6mm lenses. I would guess the most popular FPV size is 2.8mm. 2.97mm is supposed to be similar to the human eye, so you don't get fish eye, but it is a little narrow field for most people?
That said, you might get away with using a narrow FOV if you have pan/tilt servos so you can move the camera around while flying and the aircraft is stable enough and flown far enough away from things (fixed wing) that you have time to use the pan/tilt. I still would want multiple cameras with an electronic video switch (or variable zoom) to consider using 6.0mm or longer focal length.