When I was a kid, I learned that “pair” and “couple” meant two of something, and “few” meant three of something.
Over the years, I’ve seen that except for “pair,” those definitions aren’t quite true. I just ran into this example for the meaning of “couple” to be rather flexible:
Maybe you can think of some examples of vague fews.
But when you’re writing expositorily, always use “two” and “three,” of course.