Yes, it will have an effect on the network. Not sure how big, but mostly it is the price that will be affected. If he moves his coins, we might see the price become more volatile. If he says something bitcoin, the price might fluctuate a lot. After all, people will see him as a leading figure of bitcoin. Some people will follow him blindly even if he says something wrong.
Nope, he won't be able to do that unless majority of the people agrees to his changes.