I didn't notice any difference in comfort between the 23mm Corsa Speeds and the 25mm GP5000s. Maybe that's because the Corsa tires are softer than the GP5000s, which have more puncture protection. Some of the roads in the race were pretty rough... hadn't been paved in many years and lots of pothole patches. Two of my fellow racers got flats during the race.
I felt very secure going downhill on the tires. One of the descents has a couple swooping turns and another one turns onto the main road at the end. In both cases I felt very planted and gained time on my competitors -- probably because I knew the route.
I didn't use my brakes a lot during the race, but the wheels had good modulation -- I use Prime Carbon pads, which last for me over 5,000 miles / set and frequently longer. I live in an area where a typical ride will have 1,000 ft of climbing every 10 miles.