How powerful can someone be if they scaled ALL the god tier rungs? Could they than have complete mastery over there classpect ?

Complete Mastery is likely reserved for Lords and Muses. But, I mean… John made a Whirlwind that consumed the entirety of his Land before Ascension, and drilled a hole with a tornado right after Ascending. Imagine the power you could have with years of training. It is not God Tier for nothing, after all.