Guai and Cheng are two cursive calligraphy styles. They both belong to the category of Chinese cursive script. However, different calligrapher standards and personal understandings will present different styles.
Guai is a relatively unique calligraphy style in cursive script. It means that when the calligraphy strokes pass through a turning point, the direction changes, but it forms a more unique and interesting effect. The shapes of Guai's strokes vary from thin to thick, uneven in length, and sometimes have strange gaps and misalignments, but overall they present a natural, smooth, dynamic and graceful effect.
Cheng is a more common cursive calligraphy style. Its strokes are relatively smooth, regular and methodical, without too many changes and turning points. The strokes of multiplication are mainly continuous and consistent in direction. The brush will try to maintain a certain speed and rhythm when writing to make the spacing between strokes harmonious.
In general, the difference between Guai and Cheng cursive scripts mainly lies in the smoothness and change of strokes.