A problem with college scholarships is that you sometimes get locked into a major or area of study, so if you change it, you lose the money anyway.
I spent my Freshman year as an Econ / Math major, for just that reason.
There are lots of weird restrictions in the scholarship world, and you're no worse off declining a scholarship that restricts you unacceptably than you would be not having applied for the scholarship in the first place. But you have far more options in scholarships if you're applying as a high school senior planning to attend college as a freshman the following fall.
If my kid wanted to take a gap year, I'd recommend she apply, be admitted, and defer, rather than waiting to apply.
