2.1. Replacement rate provides predictability, so it's good for the economy as you know what's coming.
After that, I don't really know. It's hard to even begin the grasp what it means to "determine our own destiny", whether that has any limits, and the tensions between the individual and the collective. And who are the main actors? Is it governments or individuals? And how much power does either have to influence the population question? I think it's too complex to say there's one golden way of doing it. It might be easier if you give a certain parameters and a goal in mind.