my questuons: Hong Kong > Guangzhou > Macau

My plan is to fly from Bangkok to Hong Kong, then train to Guangzhou (stay one night), then train (or bus) to Macau, my questuons:
1) How many kinds of train from Hong Kong to Guangzhou?
2) Which station to take a train from Hong Kong?
3) Which station the train arrive/depart in Guangzhou?
4) Train or Bus will be easier from Guangzhou to Macau?
Thank you very much for your advice.
Chutima