A larger handicap number, means a slower boat.
PHRF numbers as I recall are based on a triangle (upwind, downwind, beam wind) and also locally adjusted for local wind speed range, so they are not an absolute comparison, they must be taken in context. Some boats, usually heavier ones, will be disadvantaged in light air but become relatively faster in bad weather when they can stay upright and there's plenty of wind. (Again, within limits.)
To make any boat faster, you clean the bottom. You get rid of excess weight. And you add sail area, and new sails as opposed to blown out old sails. And, of course, you learn to trim the sails for maximum speed made good on course.