Tubulars: for your type of riding you should want the lowest rotational mass for the climbs, but also consider safety on what must be warp-speed descents. Tubulars are made for this.
Look at the cross-section of a clincher rim (tubed or tubeless) versus a tubular rim. See those two 'hooks' projecting downwards off of the rim, which are necessary to hold the clincher tire... This is the problem. These hooks are heavy, at the worst possible place on a bike, they are fragile, and they are sharp and cause pinch flats. Plus these 2 rails are impossible to ride on in the event of a sudden deflation.
The lack of these hooks is the significant and insurmountable performance advantage of tubulars. Tubular rims are inherently lighter, stronger (for the same rim weight), almost impervious to pinch flats, and when the tire is glued correctly, possible to ride on with a deflated tire. I have blown tires at high speeds, and I can assure you that the tubular blowouts were far less dramatic than the clincher blowouts.
I am swapping back and forth between tubulars and clinchers this time of year. There is no performance overlap. The very most expensive of the clincher wheels are inferior to the least expensive of the tubular setups, most of which I obtained for free due to racer upgrades.
As far as tires: the best of the clincher tires are as good as the tubular tires. Again: repeat: tubulars have the advantage due to the rims.
Flats: inject 20cc of Stan's sealant in your tubular tire through the removable valve core. Use an old hand pump with the head guts removed for the injection. Your tire will now be almost impervious to all but the most extreme (tire killing) road incidents. And learn how to replace tires and glue them. Buy Mastik glue in the tins.
Enjoy.