> If you are in multiple group chats and have something to say (e.g. a life update), do you post in each individually? Or do you pick and choose which groups get the update?

Where's the problem here? Too many options and too much control? Nothing's stopping you from blasting every group chat you're in other than that you'll annoy the people in chats that don't want to hear about your problems. Maybe just send to your family and close friends.

> now some people get the same update twice - are they supposed to react in both?

This is a non-problem. Do people have to react to everything you say every place where you've said it? Is it difficult to decide how to deal with getting news over the phone and having that person announce the same news at the book club meeting? How will you know where to answer?