Carbon rims like the Enve XC or even the DT Swiss XRC330 are much stiffer than their aluminium counterpart, so you can have a 1300-1350gm wheel that is stiffer than a 1500-1600gm wheel without the noodles. Then if you spend the big bucks on DT 190 hubs, then stiff 1250gm wheels are possible.I can sure feel the difference between wheels under 1500gr and 1650gr+. The flex is very noticeable with the lighter wheels on slow steep climbs and I've bought and sold a lot for the sake of experimentation. Straightline acceleration is faster with lighter wheels but the flex on the climbs actually makes it way harder to move forward. Of course you can have a really light hub and rim but stronger thicker spokes.
Your question would be at it's place in xc racing section, as here, from what i understand. The only thing matter is weight... That why no pro bike are here. Efficiency isn't always about lightness.