Tian Yingzhang brush regular script copybook and Yan Zhenqing brush regular script copybook which is suitable for beginners? Which one should I choose?

Practice calligraphy or choose Yan Zhenqing. More formal. It's easy to write words to death when practicing Tian Yingzhang, so don't get angry. If you practice pen calligraphy, you can choose Tian Yingzhang as an introduction, which is good for font shaping.

If you really want to practice calligraphy, I suggest you find some ancient stickers to copy. Yan Zhenqing's rubbings are all good choices. P.S. recommended a website where I usually look for copybooks and materials, called bookstore. Download is free, as long as there is a network disk, and the picture quality is very high.

I hope I can help you.