A pre-competition glycogen depletion training block, where a significant amount of medium intensity training is logged in a fasted/glycogen depleted state, followed by a glycogen load immediately prior to competition is the gold standard in terms of competition preparation for sports that need a mix of aerobic and anaerobic endurance.

As for athletes that get the majority of their surplus calories from carbs rather than fat, look up various world champions and google their diet:

* Sprinters * Rowers * In-season bodybuilders * Powerlifters cutting weight for competition * Mixed martial artists

There is a bit of movement towards paleo eating in the MMA community (though oats, potatoes, rice and dairy are still typically consumed) and offseason bodybuilders/powerlifters will frequently eat a balanced mix of carbs and fat. Almost nobody at the top levels does low carb/high fat though.