I have many snakes in my area. Cottonmouths are killed with impunity and yes, they do have a distinct odor. Copperheads are given a pass if they go the other way when I see them. The same goes for rattlers. The rest aren't poisonous and are free to do whatever they do. However, if any one of them tries to bite me, they die.
My count since moving into the new house is about 10. Most were cottonmouths. One was a water snake that decided to get pissy with me while I was minding my own business, sitting in a chair. Another memorable one was the copperhead that wouldn't let me pick some tomatoes for dinner. The only rattler I have seen was only about 2 feet long. His problem, however, was that he decided my back doorstep was his. I chased him off 3 times before I decided that it wasn't worth the risk.