My favourites are 1.5 to 2.5 inches with a block heel. I will wear a well-designed kitten heel (the Okalas) but it's not as practical given the sidewalks where I live, so it tends to be relegated to dressy occasions.
I can go up to 3 inches and even walk quite a lot, assuming the last is the right pitch and heel is stable enough. I *never* go over 3 inches. Super uncomfortable for me.
I can also go down to a sneaker *if* and only if I change up the insole for something with more arch support like Superfeet. That's what I did with my Eccos and I love them.
I regularly wear a 3/4 inch lug sole boot as well but I need extra heel protection for my plantar fasciitis with those.
In some ways I think it is difficult to generalize about heel height because other features of the shoe may make it more or less workable. Not just the shape of the last, the padding in the insole and the pitch, but also support at the top of the foot. Booties, lace ups, boots, and sandals tend to work better for me than low vamp shoes because I don't have to work so hard to keep them on my feet.
Some current and recent winners below: