بسم الله الرحمن الرحيم
If the Barailavi imam has shirkiya beliefs then it is not correct to offer salah behind him. And if he does not have shirkiya belief then salah shall be valid behind him, but such a person should not be made imam permanently. The imam should be one who has correct beliefs and who practices sunnah completely.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.