I will just state my opinion as well, the more the better right?

1. a 10g is perfect for a hatchling
2. a 20g will be fine for any snake under 2,500grams.
3. I haven't noticed a difference
4. As others have said, leave your new baby alone a week after bringing him/her home. I would begin handling a few times a week for 10-15 minutes. Just make sure not to handle for 2 days after feeding. They don't really "enjoy" being taken out and held they just tolerate it. If you are taking care of your baby the right way then there should be no problems with a timid or aggressive snake.