A lay individual is not qualified to determine the most knowledgeable in the right way without referring to whoever can determine him amongst the experts, since they– and not any inexperienced person – are the ones who know the level of knowledge of the people that reached the level of ijtihad.
It is permissible for the Muslim woman, whether she was from a Sayyid family or not, to marry a Muslim man even if he used to follow another religion, but it should be with the consent of the father of the woman if she is a virgin.