السلام عليكم ورحمة الله وبركاته May Allah protect you ya ustadh and reward you. Do we consider the Ashariyyah as kufar or not? Because there are statements of big scholars which state that. And can we pray behind them or behind a sufi or other wrong aqeedah?

Ustadh AbdulAziz al-Haqqan

They are not disbelievers may Allah protect us and you from making takfeer of the Muslims. Praying behind them is correct. The sahabah prayed behind the kharijites, so take it as a rule that praying behind the people of bida' is correct.