High crown depends on the shape of your face in my opinion. What looks too high on other is sometimes too low for my taste. I measure by open crown (hat popped out with no creases) and for me a high high crown is six inches... that is the highest I have seen in vintage fedoras.
Lower than low I have seen crowns that are four and a half inches open crowned, at my guess.
Best example I can give is to show you people wearing the hats
Lower crown BB
Higher crown JC
You see Jimmy Stewart wearing low crowned hats in some of his 1930's movies, and you also see him wearing high crowned hats that have been pushed down. You'll figure out what looks good on you after some looking around.