What is the ruling on the imamate of a smoker who does not pray Fajr on time, especially when there is someone better than him in memorization of the Qur’an and voice?

An Imam should be appointed for the congregation. It is preferable that he be the one most knowledgeable of Allah's Book (the best reciter), or the one with the best voice if that brings humility and comfort and does not compromise the recitation, while it is permissible for a superior person to pray behind an inferior one. It is not permissible for a person who does not maintain the Fajr prayer at its prescribed time and with the congregation, and who smokes, to lead you in prayer. This is because the Imamate is an honorable position, and only a pious and committed person is fit for it. He should be advised gently and wisely to quit smoking and maintain prayer.