Route planning

Hi! I would like to explore this route by myself and I have some questions.

Get off at Nan Hua Yuan San Qu of Huairou, then walk on about 100 meters and connect bus H21 at Nan Hua Yuan Si Qu to Shuichangcheng (water great wall). The bus runs every 40 - 50 minutes. You can also take a taxi to the attraction, costing about CNY 150 per cab.

How long would the journey on H21 take? Google shows me that it will take 5 hours?
How long would the taxi ride cost?

Also, if I am planning to stay in the Huairou area to take this route, which is a recommended area to stay in?