any case studies / anecdotes of people significantly upping their agency in their 20's?

feel like i had a huge jump when i was 18 and a slow climb but just been.. doing life recently

start a startup, have kids, do things that could kill you. take more and bigger risks. its your birthright and the reason you were put on this earth

Agree with this. I'd just stick a caveat on that having kids/getting married adds dependencies so risk tolerance might change after the fact. If you have no dependencies, go for gold.