Well with human heat pads you don't have a choice of three. You controll it 100% percent with a thermastat same way you would flexwatt. I can have a 85 hot spot, a 90 or 92...whatever. So for control when used with a thermastat or control device, it works perfectly.
I have never even had a slight issue. But again millions of things work, and ANYTHING can cause a fire.