Gearing combos?

Has anyone tried to find the ideal gear inch for the various gradients on the island. Obviously I go big ring-11 on the steepest climbs but was not sure about the slightly downhill sprints, like the green jersey sprint going counter-clockwise. If you’re going downhill does cadence matter more than speed (i.e. rear tire rotation.) I seem to do well in the climbs but get dropped on the flats and downhills. Also I use a kinetic road trainer with garmin cadence/speed sensor.