You can chose different tangs.
I have a blue, yellow and tomini in my 125g. The bristletooth tangs need only a 75g tank or so, as well as the Kole tang. Have you looked at the tangs at Aquarium Fish: Tropical Freshwater Fish and Saltwater Fish for Home Aquariums
? Lots of choices there and ideas.
I don't think it will suffer for awhile in a 100g tank, but at some point it will get pretty big and that might be when you need to explore upgrade options.
Theres a lot of opinions on tangs and tank size, me, I like to err on the side of caution, I don't want to cause a fish to suffer cause I "want" one LOL. But if your stocking isn't bad and you have the proper tank parameters there's no reason why you can't have a tang.