Please advise me on using subway from baiyun airport to guangzhou hotel or landmark hotel.

Hi, the former hotel you mentioned is Hotel Canton at Beijing Road, right? If so, you can go to Airport South MTR Sttion to take subway line 3 to Jiahewanggang. Then transfer to subway line 2 to Gongyuanqian Station. Getting out of the MTR station, you can walk to the nearby Beijing Pedestrian, which is within several-minutes walking distance from your hotel. While, for Landmark Hotel Canton, you can also take the same way, but you need get off at Yuexiu Square and then walk to the hotel.