There are two buses from Guangzhou to Nanjing every day: 5222 will be faster.
The information is as follows:
Train number 1312, general express, new air-conditioned Guangzhou departure time 20:05, arrival time in Nanjing 04:39 on the 3rd day, 32 hours and 34 minutes, hard seat 209.0, hard sleeper 401.0 Soft sleeper 629.0
Train number K222 Fast, new air-conditioned Guangzhou driving time 09:29 Arrival time in Nanjing 12:47 the next day 27 hours and 18 minutes Hard seat 332.0 Hard sleeper 379.0 Soft sleeper 584.0