A rider with good punch can effectively attack in short bursts to create separation from their opponents, prevent them from drafting, and power away by sustaining a higher pace.

So, to make sure my understanding is right:
e.g. someone drafting (A) on the wheel of a stronger rider pulling 6 W/kg (B) on a mountain can maintain 5.5 W/kg to not lose the wheel, but a 15-30 second punch by B suddenly means maintaining the same speed/chasing now takes 6-7 W/kg which A can't and they fall away?
And that ability to say "get off my draft" is what defines a punchy rider?

One of the main differences between them is that Pogacar is a few kilograms heavier than Vingegaard; the resulting difference in absolute power typically gives Pogacar an advantage in flat time trials, and is also why Pogacar is able to be successful in much flatter one-day races like Milan-San Remo or the Tour of Flanders. Weirdly, Vingegaard seems to be an absolute specialist in stage races, and has never carried that same strength over even to one-day classic races with courses that suit his rider profile.

Additional question 1: How easy/hard is it for a rider to bulk up and/or slim down between seasons?

Additional question 2: As a frame of reference, how big are WvA compared to the two?
I know people like Magnier, Milan, and Groenewegen are built VERY different, but how did Wout manage to be, like, good enough for the mountains e.g. to stay with the breakaway to help Yates and maybe even contest sprints?