Did each of the twenty narrators gather the Qur’an according to the language of his people, in conformity with the seven ḥurūf, or did the reciter from whom he narrated impose the narration upon him?

The narrators of the ten Qira'at (readings), including Imam Warsh, did not play a role in the collection of the Qur’an. Rather, their role was to memorize, verify, perfect, and transmit the readings from their teachers. Warsh learned the reading from Nafi’ in Madinah, completing four full recitations with him. He also learned from him the rules of Imalah, Taqleel, and Fath, and transmitted them to those who learned from him. There is no objection to Warsh having learned Imalah from those he recited to before Nafi’, as Imalah is part of the seven Ahruf (modes) in which the Qur’an was revealed.