From the perspective of smooth and beautiful daily writing speed, whose copybook is the best?

I recommend you two. I personally like them. They are fluent and beautiful, and they are famous running scripts. Yan Zhenqing's Sacrifice to the Nephew, Mi Fei's Susu Post and Tiaoxi Poetry Post.

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Supplement: Actually, the soft and hard strokes of calligraphy are the same. The most important thing is that the structure of Chinese characters is accurate and the strokes are in place. These are the same things as soft and hard calligraphy. Post first, then post silently, and then combine to read posts. Hard pen can also consider Pang Zhonghua's running script.