Why would you need any filter with supposedly treated municipal water??? It's already treated.
Buy a softener to remove the hardness and be done with it.
Impurities (sand/particulates/turbicity/tannins/cysts/etc), chlorine/chlorarmines, lead, arsenic and the ever dangerous possibility of a Japanese midget submarine slipping through. They (government) treats the water to hopefully make it through the distribution system. What is at your home entry? Do you actually trust the government (Flint)?
Why a water softener if no hard water?