Is it permissible for an ordinary person to receive religious knowledge from Salafis and Ash'aris, while avoiding delving into matters of disagreement between them, or to choose not to favor any opinion in controversial issues given his ignorance? And does that affect his Islam?

A beginner student of knowledge should avoid the books of the people of innovation (Ahl al-Bid'ah) and restrict themselves to the reliable books of Tafsir (Qur'an exegesis) that adhere to the methodology of the Salaf (pious predecessors). They may benefit from the books of the Ash'aris in matters where there is no disagreement with Ahl al-Sunnah (Sunnis).

As for the controversial issues that must be learned, the truth regarding them must be ascertained by referring to reliable books of Tafsir, asking trustworthy scholars, and supplicating to Allah for guidance.

As for what does not need to be learned, there is no obligation to investigate it thoroughly. Ibn Taymiyyah clarified that what is obligatory upon a legally responsible individual in terms of belief is faith in Allah and His Messenger, and affirming all that the Messenger brought, generally and in detail, according to what reaches them. It should be noted that what is obligatory upon scholars in belief differs from what is obligatory upon common people, and that faith and disbelief are determined by legal proofs, not merely by rational analogy.