Two white/two red give a 3 degree path. If you go to one white and three red, that is a 2.8 degree path with most PAPI, VASI installations. The 3 degree standard installation should give you a visual height of no less than 25 feet above the threshold. Some give you more depending upon the airport requirements.
Is there a gain going to three red? At proper approach airspeed, it will give you a touchdown approximately 500 feet short of the touchdown blocks, or about 30 feet over the threshold.