I googled Chaim Potok and according to Wikipedia, he was raised Orthodox and became a Conservative rabbi. Someone like that is someone whose perspective on Chassidism or Charedi’ism is not going to be accurate and is not going to be something we would want to be influenced by.
If I am not mistaken, Rav Moshe Feinstein, zatsal, wrote that Conservative Jews are apikorsim (meaning those Conservative Jews that actually know what Conservative hashkafa is and believe in it) even if they are tinok shenishba (even if they as people are blameless, the fact is that their beliefs are kefira).
According to that, it would seem that CP would qualify as an apikorus, and in any case, his beliefs were kefira. The purpose of his novels was to present his hashkafos regarding Orthodoxy and these hashkafos are kefira.