There are numerous varieties of holly. The mst common around central Texas is Yaupon Holly which is generally too big to be a bush and too small to be a tree. I have seen a few that are almost a foot in diameter and over twenty feet tall. There is also a Dwarf Yaupon Holly that is used as an ornamental and it rarely gets over five feet tall, but then they are generally pruned to keep them more dense and compact. I have seen a few American Holly trees, but they are apparently fairly rare here. The ones that I have found are in moist heavily wooded areas. The American Holly is a true tree and has a tall straight central trunk and has a cone shaped canopy. I am sure that they can get very tall, but the ones here are less than forty feet tall.
I certainly would not consider cutting down an American Holly just to get some turning wood. Supposedly, holly is the whitest of all woods. I don't know if that is true, but I know that the Yaupon Holly is the whitest wood that I have seen. It does not have a distinctive grain pattern and it has a bit of a tendency to split s it dries. I believe that the wood of all hollies have similar characteristics.
BTW, I'm with you, it would be my absolute last choice for a peppermill.