Is it permissible to pray behind a Sufi imam when most of the congregants are Sufis?

The rulings for praying behind a "Sufi" are detailed based on their condition:

1. If they are a Muslim with sound belief and adhere to the Sunnah, then it is permissible to pray behind them, even if it is preferable not to call them a "Sufi," because Islam encompasses asceticism and righteousness. 2. If they hold corrupt beliefs that take them out of Islam, such as believing that the dead can bring benefit or harm, or claiming that saints know the unseen, then prayer behind them is not valid. 3. If they are openly engaged in innovations that do not take them out of Islam, it is not permissible to pray behind them unless it is impossible to find another imam or move to another mosque, this being to preserve the congregational prayer.