Which circle picks a circle leader & defines the sub-circle aims? What are the pros, cons and tensions of different options?

In SoFA’s website circle, during a new sub-circle formation, we realized that there are two different ways to form a circle:

Either from the bottom up with the circle convening and then bringing the circle information like leader & aim/mission to the parent circle for consent, OR from the top down, define these things in the parent circle and bring them to the convening of the sub-circle for consent.

But here’s the main question:
What are the pros and cons of each?
What if it starts one way, but then there’s tension to change it?
How is that naviaged?