There are not many people around 2.7. Compared with the peak period, because the most people in Shenzhen Bay are through trains from the airport or other places in Guangdong, there are not many people going directly to Shenzhen Bay.
Regardless of the price, I don't know the difference between a taxi and a bus. A taxi may be faster. After all, the bus stops at the station. And if you plan to arrive before 7 o'clock, the bus may be inconvenient.
There is no need to buy a full-time pass if the return trip is only from Luohu. One-way return to the subway is 35 Hong Kong dollars, and it doesn't cost much to take the subway in Hong Kong one day. It is not uneconomical to buy a full-day pass to and from Luohu or Lok Ma Chau.
The population of Luohu Port is the largest among all ports. Generally, one-hour customs clearance on both sides is relatively smooth. In the worst case, the two sides may add up to three hours, and the Lok Ma Chau Control Point is similar. If it is faster, it will be the fastest in Shenzhen Bay.