Hi I arrive 5pm in HKIA and need to go to Tianhe Guangzhou. Would you recommend Bus or Train?

Since you reach the airport in the afternoon, you can take the direct shuttle bus to China Hotel, Garden Hotel or Landmark Hotel.
Upon reaching Landmark Hotel, you can walk to the Haizhu Plaza Station to take the subway line 6 to Tianhe area directly.
If you reach the China Hotel or Garden Hotel, you can walk to Yuexiu Park Station to take the subway line 2 to Haizhu Square Station and change to line 6 to Tianhe area.