All of the chinese players are playing DHS rubbers on their forehand. These rubbers are pretty hard, they are getting eventually softer of tuning but not a lot. The sponge hardness of them is about 38 - 41 degree chinas scale. This would start with something like Xiom Vega Pro and its just getting harder.
On the backhand its personal what they like and prefer. Some players are prefering medium rubbers, some of them more hard rubbers. But im pretty sure none of the player plays a really really soft rubber like T64fx on the backhand, the softest should be something like T05fx soft-medium.
The reason for the forehand is because as harder the rubber as more speed you finally get. This is not like each rubber in the world works but the chinese rubbers should work like this. On the other hand the rubber cant be too hard otherwise you couldnt play with it.