The difference is:
First, lower case is a kind of regular script, and regular script includes lower case;
Second, the font size of lower case is generally 1~3 cm, and the font size of regular script is not limited, ranging from 1 cm to several inches.
Third, the pen is slightly different, and the fine print should be round, beautiful, straight and neat; The capital letters of regular script should be dignified and heavy, with the reverse side (hidden front) when writing big and the front side when closing the pen; ; You don't need to use a sharp point when writing lower case letters, but you should use a sharp point and use a pen or signature pen when collecting pens.
Extended data
First, regular script, as it is commonly said, evolved from Han Li and can be divided into Weibei and Tang Kai according to different periods. Weibei is a transitional body from official script to regular script. Regular script in a narrow sense refers to Tang Kai, which gradually matured after the Tang Dynasty. Its representatives are Ou Yangxun, Yu Shinan, Chu Suiliang and Xue Qi in the early Tang Dynasty, Yan Zhenqing in the middle Tang Dynasty and Liu Gongquan in the late Tang Dynasty. We often say that the top three of the four masters of regular script "Yan Liu Ouzhao" were in the Tang Dynasty.
Second, lower case, as the name implies, is the smallest type of regular script, which was founded in Zhong You of the Wei Dynasty in the Three Kingdoms. He was once an outstanding master of official script, and the brushwork of regular script was born in Han Li. His brushwork is as vivid as playing in the sea. However, the structure is wide and flat, the horizontal painting is long and the vertical painting is short, and the legacy of official division still exists. However, the model method is ready, and it is actually the ancestor of the official book. When Wang Xizhi arrived in the Eastern Jin Dynasty, he studied the lower case calligraphy more carefully and made it perfect, which also set a good appreciation standard for China's lower case calligraphy.
Three, under normal circumstances, people call block letters more than one inch and less than a few inches block letters. The larger characters in real books are called "Bangshu" and "Broken Book". According to the accumulated experience of calligraphers in past dynasties, learning calligraphy should start with writing big characters and doing basic exercises. Mastering the stippling, structure and white cloth in block letters, and making stippling accurate and proper, then writing in block letters can be comprehensive and the stippling rules are clear; Moreover, the study list can be intimate, open-minded and not distracted.
References:
Baidu encyclopedia-regular script