PAA: The Beis HaLeivi, I think, was the one who said you need a Mesorah, and he brought Ra’ayos for it.
TU731: The “do you think you understand the Sugya better than…” argument is not an argument. By that logic, you should never say P’shat in anything, ever, because you don’t know better than everyone who has ever spoken on it ever. R’ Chaim (if he actually said this; I’m not holding in his Shittah here) is entitled to his opinion even if it argues with many major Shittos. Us Talmidim are entitled to point out that he is arguing on said Shittos and in the minority. I could respond to your R’ Chaim quote with, “Do you think you know the Sugya better than the Maharal to say anything to the contrary?” It’s inane and doesn’t mean anything.