Layering the hair

Q: Can women keep their hair 2 lengths? They call it layering. According to what I heard from one Aalim is that Nabi (s.a.w) prohibited from qaz (shaving the sides and keeping the hair big on the top), but to have a small difference is ok. For example to cut 4 on the top and 3 at the bottom. So my 2nd question is that is the fatwa that we generally learn from our ulema regarding males is on a precautionary/taqwa basis?