"Zi" belongs to everyday words, and "a good word" should be beautiful and easy to recognize, which is the basic requirement for the writer and his words. It can be seen that the word "word" focuses on practicality.
"Calligraphy" is an art based on "good characters", which can be integrated into the artist's understanding of life (for example, Wang Xizhi learns calligraphy and watches the white goose sword dance; ), emphasizing the publicity of your personality.
Therefore, calligraphy works, especially cursive scripts, are often "dragon and phoenix dances". Of course, the "dragon and phoenix dance" of characters still has to follow some rules of calligraphy and writing, which is not so completely random.
I wonder if my explanation is satisfactory.