Honestly, how does education in top schools differ from education in less prestigious colleges?

I was recently accepted into a top school like you wrote and feel that you should pick a school that fits your learning style and the kind of environment that suits you. While you said you mostly only care about academics, human beings are not robots and unfortunately, you will not be able to attend a top school if you portray yourself as only an academician.

As you already know, with admit rates between 3 and 6% for top colleges, 94-97% of most qualified applicants get rejected. It's not because of their GPAs or Test Scores or Course Rigor but usually, they are not a good fit for the college that needs are a variety of interesting people to fill various jobs and roles in their freshman class. These are empty seats in the orchestra or jazz band, justice warriors, ballerinas, lacrosse, and tennis players, and Malalas and Gretas in the making. Colleges themselves determine who gets in and who doesn't so you can't really shop for college based on academics because the system doesn't work like that. It's the opposite, if you impress them as a multi-dimensional creature who has talents and skills that fit their needs and goals, they'll let you study whatever they offer, and even make an exception.

In my opinion, the most meritocratic schools would be MIT, CalTech, UC Berkeley, Georgia Tech, Carnegie Mellon, Rice, JHU, or anything similar. At STEM-ish schools, there is less emphasis on needing recruited athletes, legacies, or development candidates so whether you get in or not will bear heavily on your academic narratives, honors, awards, competitions, and intellectual clout. That is why standardized test scores at some of these schools are even higher than the Ivy League.

They are also more cutthroat (your expression). For example, if you want to major in CS, and get into Carnegie Mellon, well, you are not going to be the smartest person in your class because everyone is a computer genius. That is why they are number #1 in CS. So that is a cut-throat environment because there are cohorts in the CS class that can solve a Rubik's cube in 7 seconds and recite 100 digits of Pi backward.

With the exception of both Columbia and UChicago's Core Curriculum, I don't think any of the Ivys' or Elites would be as hard as their peers because most of them have an open curriculum and you can pick and choose what you like and have multiple concentrations. A Columbia/UChicago regardless of whether you are Gender Studies or Physics/Math major, you have to do the core. And for some people, the Core is a brutal undertaking.

The hardest colleges to get into are not necessarily the hardest colleges academically because the schools themselves fully expect their cohorts to be well-rounded humans when they occupy their campus. They don't want to admit students who just go to lectures, study, get good grades, and repeat the process for 4 years. They expect them to grow into their best version of themselves by doing things outside of their comfort zone. This could be done by, say joining the improv comedy group, being a writer for a political satire magazine, tutoring low-income kids at a non-profit, joining a rock climbing club, an acapella group, a cooking club, getting involved with the community garden. The reason they want multi-faceted admits is because there are an infinite amount of resources and opportunities at top colleges to experiment with yourself and they encourage this. At Yale, for example, they expect you to study a year abroad fully immersing yourself in a foreign culture and language. Why not? The best schools want you to join social clubs which even include Greek life and secret societies. They want you to meet up with friends for late-night chicken fingers and beer in the butteries. They encourage you to go to movie nights or costume parties, soirees, and formal balls. This is what life at a top school is about in my opinion, not just about acquiring academic knowledge.

So, if you're gung ho about pursuing your Ph.D. even before you've had an opportunity to grow up into a complex human being, I think it will be challenging to pick a list of colleges that will embrace your surgical approach toward achieving your academic goals.

Originally, my dream school was MIT because I thought a lot of interesting quirky people attended but I'm glad I'm going elsewhere because I don't think you get a lot of academic support at MIT, and 1/2 the students seem to struggle with untreated mental illness. With the exception of East Campus, I don't think I would like MIT very much.

Good luck.