What is the ruling on studying the Shafi'i school of thought and reading Sufi dhikr for someone who is Sunni?

The Imam Al-Shafi'i is one of the Imams of the Sunnis, and studying his madhhab contains great good. The student of knowledge should read the books of the Imams of the Sunnah and those concerned with supporting it, and avoid reading books that contain violations of the Sunnah or deviant sayings, especially for those whose feet are not firmly rooted in knowledge, lest their hearts be affected by those delusions. As for those firmly rooted in knowledge, they can take what is good and leave what is bad.