Nanning is interesting.
They are building a subway last time i was there a few years ago.

Very close to Vietnam n their mandarin accent is so different from the north.
Lots of scooters around like those in taiwan or vietnam, quite unlike shanghai.
The southern chinese food is good too n much cheaper than in pvg.

Didnt get to visit the beach area but heard it is nice.
A few hours away by train/bus.