Walk from Tsim Sha Tsui to East Tsim Sha Tsui Station, then take the subway to Hung Kan, and then take the subway from Hung Kan to Lo Wu to cross the border. About 1 hour.

Taking a train from Shenzhen to Guangzhou East Railway Station takes about an hour.

Take Metro Line 3 from Guangzhou East Station to Airport South Station, which takes about 40 minutes.

That is, the entire trip takes about 3 hours.

I went to Baiyun Airport via this route last weekend, and the time was easy to control. If there's a traffic jam on the bus, it's hard to tell.