They can also control and manipulates air, whether creating whirlwinds or breezes. Many fast-flyers have larger wings, but this is purely aesthetic, as it matches their talent and doesn't make them fly faster.
The fast-flying-talent fairies do not really have an explained role- they are simply the fastest fliers (which comes in handy during some adventures for certain). They also are wind elementals of a sort, creating small tornadoes, making cool breezes, and blowing things down.
Vidia, the fastest of the fast-fliers, is the only one of any major importance, though Wisp was created for the books and was focused on in one chapter book.