What is the most convenient way to travel from Houjie Town to Kowloon?

I need to go from Houjian Town in Dongguan to Kowloon in the late afternoon of April 26 (Friday). I can leave Houjian Town at about 4:15pm. I was told that I can (1) take a car to go to Changping train station, then take a train to go to Kowloon; or (2) take a car to Luohu Port, and go to Kowloon. Which way is easier? Do I need to buy a train ticket in advance, and if so, how? I hope that the train ticket will have guaranteed seat, is that true? From Luohu to Kowloon, is that by train or bus? How often does the train (or bus if applicable) run in the evening hours? Thanks.