Yes Liam’s backhand is incredible! He firstly has a very relaxed arm which allows him to accelerate very well into the ball without loads of effort. The key areas to this shot are the forearm and especially the wrist which is used to brush over the ball to create spin but also to whip through the ball quickly on contact.
Liam also has brilliant timing where he strikes the ball right at the top of the bounce if not just before which means his opponents have much less time to react. To play these types of backhand you need to practice being relaxed and playing with a high arm speed and a low amount of tension. Try to focus on having a closed bat angle and getting the feeling of really brushing over the top of the ball to gain more topspin as well as having a fast recovery to be ready to play the next ball.