Two questions: Do I need a visa to fly from S.Korea to Macau? And train from Macau to Guangzhou?

I'm a US citizen. I will be visiting South Korea for a few weeks. During this time I have a 3-day business trip in Macau.
QUESTION 1: Do I need an entry permit to enter Macau from S.Korea or is my US passport sufficient?

After Macau, I will take a train to Guangzhou for 3 days visit.
QUESTION 2: Will I need an entry permit to enter GZ? If yes, what kind?

Thank you in advance.