All Torah is learned only with Divine Inspiration (what you would call Ruach HaKodesh), as it connects the Yid to his Source.
If it is not learned as a connection to the Source, rather as a subject, then that (seemingly) IS Apikorsus.
I like your “trying to define a gadol” statements: I do have issue with one minor point:
That is pretty much unanimously the derech of the Chofetz Chaim, Rav Chaim Brisker, and their great contemporaries.
Chassidim, Sephardim, Yekkies, etc. do not hold of or follow this derech. I would be very wary to exclude most of Klal Yisroel.