How does the GB micromanage the lives of JWs?
Answer: Any way they can.
A better question might be: In what areas does the GB not micromanage their lives?
Despite the oft quoted phrase "matter of conscience" that you occasionally find in the Watchtower, there are precious few areas where those crochety old men don't intrude. Diet. The consumption of alcohol. The decision to use contraception. These are the only places I can recall where JWs are actually allowed to think through an ethical dilemma using their own brain; though I anticipate that the GB will eventually get around to shoring up these holes in their net of control (it's not like they have anything better to do). Even completely non-ethical issues, like dress and grooming, are decided for JWs in advance. Everything not forbidden is compulsory.