This is so variable by major. And for a college (like Brown) where you don’t apply or declare a major freshman year- the “data” is really of limited utility.
At Cornell the largest class over the last several years has been a Psych course (social science, not STEM). At Brown in my day, the biggest classes were Poli Sci and Literature- because of superstar professors. So knowing that the Bio class that all the wannabee premeds is large– helps the kids who have no intention of taking that bio class how???
People on CC really idealize small classes (more so than in real life) for reasons that I don’t understand. My MIT kid had huge classes for the required core and often tiny classes for the “required” HASS distribution courses (you pick your own, but the university determines how many of which type you need to take). He had strong relationships with the professors in both types. And of course- by junior year, virtually all his classes were small. But this is only one piece of it. The professor who supervised the research project he worked on, the professor who accompanied a group on a summer fellowship program and bonded with the team- both in a supervisory capacity and socially, the professors he met as part of an EC, and the professor who was his advisor/thesis mentor– he didn’t have courses with any of these.
When a research spot is posted there isn’t a requirement “must have a personal relationship with the professor” before they’ll consider you. There will be a paragraph or two of the actual requirements- technical lab skills, computer languages, hours and times you MUST be available for team meetings, etc. But they aren’t sticking your resume into the “professor likes this kid” and “professor has no idea who this kid is” piles.
Major in philosophy- your classes will be small. Major in CS and at least for two years your classes will be big. Take any of the courses to meet the med school application requirements- they’ll likely be big until the dropouts begin.