So, the impression I have, based on casual conversations with friends who are professors at one of those “elite” departments of a high-ranked university, the general university admissions prescreens applications based on the usual metrics, e.g. grades, test scores, etc. and then passes on those meeting that criteria on to the admissions committees of the departments, who study the applicants more in detail and do the selecting at the individual level. One professor in the school of engineering told me that by the time the filtered applications got to him, he could basically disregard the GPA and test scores because they were all the same. In all my conversations, I never got the feeling that there was any complex “formula” at play. It sounded all very subjective and, in fact, the professors do have personal opinions about the kind of students they want to see in their classrooms, and it’s not always the ones with the best grades/test scores.
Obviously, this is all anecdotal but what it says to me is that applicants should be cognizant of the minimum bar to be seriously considered but once they’ve reached it, forget it and go do the things that interest them. The admissions committees are made up of people just like us.