Let me talk about my understanding. In terms of exploration potential, there is no doubt that Wei stele is better than Tang Kai. However, among the masters of stele writing in the late Qing and early Ming dynasties, all of them were proficient in Tang Kai. Therefore, we must first lay a good foundation and practice Tang Kai well. Yan style is the pinnacle of calligraphy in the prosperous Tang Dynasty and has a profound influence on later generations. However, in the late Tang and Five Dynasties, many people held critical and negative views on Yan Zhenqing's calligraphy achievements. For example, the well-known later master Li Yu believed that Yan Kairuo crossed his hands. The original sentence may not be correct. It was not until the Song Dynasty that Yan Kai gradually gained people's recognition and respect. Moreover, the understanding of Yan Kai in the past dynasties is also different, such as Cai Xiang, Zhu Zhishan, Liu Yong, Qian Feng, He Shaoji, Tan Yankai, Hua Shikui, etc., especially the last four, starting from Qian Nanyuan, it can be said that there are several Everyone who is truly successful in learning Yan Kai.
As for the choice of Yan Kai’s post, according to my understanding, "Duobao Pagoda Stele" is in Chinese regular script and was written in the year when Lu Gong was not confused. The writing style has many traces of Chu Suiliang, Ouyang Xun and Yu Shinan in the early Tang Dynasty. In addition, Yan Zhenqing's own style is included, so it is a Chinese regular script that is worth learning. It is also very beneficial to further study of Xingkai script, such as Huairen's Collection of Characters, Sacred Teaching Preface, and Zhiyong Zhencao's Thousand-Character Classic.
As for the "Qinli Stele", I don't like it very much, especially after comparing it with "Ma Gu", "Li Xuanjing", "Yanjia Temple" and other steles. Most people in the world call the "Qinli Stele" the authentic one of Yan Kai. It is ridiculous that the stele has only been reappeared for a hundred years. No one who has studied Yan in the past has seen this stele or been influenced by it. When it comes to the artistic value of "Qinli Stele", I think we should contact "Zi Shu Gaoshen" and use Gaoshen's writing style to write the "Qinli Stele". Maybe there will be some gains, but the so-called horizontal thinness and vertical thickness are the authentic ones. The beautiful Yan Kai makes people smile.
If you want to learn Yan Kai, it is recommended to first study "Zi Shu Gao Shen Tie", draw the lines with the elbow hanging at the center, and experience the beauty of his pen. Such as gaining momentum in the air, and the explosive power of cutting forward. After some time, choose a Yan Kai stele book you like and contact it. I recommend "Magu Immortal Altar Story" and "Yanjia Temple Stele". The former is powerful and the latter is rich. In addition, you can also refer to the copies or works of calligraphers of the past dynasties, such as Qian Feng's works, Tan Yankailin's 125th Announcement, He Zizhen's works, etc.
At present, I only understand the above level. Several knowledgeable book friends have recommended "Zhushan". I think the beauty lies in its naturalness and clumsy taste. He Zizhen's works are considered to be Yan Kai wrote it best, and he exaggerated the characteristics of the outer extension and the inner palace vacancy very well. If you have the opportunity, you can read his works for reference.
I hope it will be of benefit to the original poster, and I wish your calligraphy art will continue to prosper.