Any U which has a program for grad school is going to offer MORE opportunities than you can possibly take advantage of as an undergrad. You are going to need the core foundational courses regardless of where you go. And your Duke professor is likely to have colleagues at 30+ institutions, any of whom will have research grants and labs and ongoing projects for you to participate in.
Relax, you’ve got this. Let the results come in. But if you already have been accepted to a U which is affordable, the rest is gravy. You do NOT need to major in computational biology-- it is way too narrow a field for a HS kid to decide “this is my ride or die”. Most of the current faculty and researchers in the field did not major in it, right? And they are still doing groundbreaking work. How is that you suppose? They majored in plain old vanilla bio; they took as much CS and applied math as they could handle; they worked as hard as they could to get into solid grad programs where they could collaborate with colleagues in genetics and chemistry.
You do not need to specialize right now. And if you got into U Michigan- what a fantastic result. You are off to the races!