Questions are some of the best contributions here
I agree that a molle isn't a great beginner bow. I've seen people do it for their first, and I have only ever broken a molle because of a bad saw-- but those people don't seem to make the molle completely mollegabet-like with thick levers and three inch wide working limbs, and I didn't try until my tenth bow and got lucky enough with my first to get it down pretty well.
Molles are my favorite bow to make. I can rough and tiller them much faster than I do other bows because I'm comfortable working the shorter working limb and refining the levers with my machete, where with flatbows I tend to switch to my rasp with a whole eighth inch to remove before I hit my target weight and the outer limbs are too stiff
I don't know for sure if cited mass efficiency actually translates to better performance, but it makes sense. those levers, when worked properly, are lighter than working limb would have been, so they should offer less resistance when the inner limb does the work of a full limb, and that aught to translate to higher arrow speed-- I think
I
do know for sure a good flatbow or pyramid is great better for learning to tiller, and tiller is way more important than crunching mass efficiency. Drink some milk and grow a bit before taking the ice cream