Are there sects other than the four schools of thought that are considered among the Ahl al-Sunnah wal-Jama'ah? And do the books "Fath al-Bari Sharh Sahih al-Bukhari" and "Sahih Muslim bi Sharh al-Nawawi" include all the sayings of the Ahl al-Sunnah wal-Jama'ah?

The four schools of thought (madhahib) are not sects, but rather jurisprudential schools that differ on ancillary issues, not fundamental principles. Within the scope of Ahlus-Sunnah, there are groups that differ in the priorities of da‘wah (proselytization) and reform. The books "Fath al-Bari" and "Sharh Sahih Muslim" are two excellent books by authors from Ahlus-Sunnah, and they may transmit the sayings of the people of falsehood in order to refute them.