The technology trip. Huaqiangbei is nine square blocks of component suppliers, assembly floors and showrooms where a product goes from a bench to a pallet. It is not a mall and it does not behave like one; it needs someone who speaks the trade, knows which building has the counterfeit problem and which has the real engineers, and can get you into a supplier meeting with an hour's notice.
The family trip. Shenzhen's theme-park cluster in Nanshan does the impossible — Window of the World at scale, Happy Valley for the coasters, and OCT's eastern town for the slow evening. Add the Safari Park and the bay boardwalks and three days go quietly.
The city trip. Shenzhen has an honest thirty-year museum, a coastal art district in Old Town, the Hakka walled village at Gankeng with its lantern festival, and the Shenzhen Bay boardwalk for the sunset with the metropolis behind you. It is greener and more walkable than its reputation.
And then the border
Futian and Luohu crossings both connect to the MTR and, at Futian, to the high-speed line. Used correctly, Shenzhen becomes the mainland half of a Guangdong plan — Hong Kong for a day, Macau by ferry, Guangzhou for dim sum and the Cantonese opera museum.