I think my personal experience can shed light on this. If I could post it anonymously, I would.
I was forced by school administrators to take an IQ test in high school because I cut so many classes and almost failed math. I never opened a book because I didn't care about school when I was 16. I took an IQ test administered by the school psychologist and scored 140+ on the Stanford-Binet scale, which they call "very advanced or gifted." My memory scores were 99.99%ile, as were my verbal scores. My performance IQ was my weaker area (mental calculations, etc.).
I'm now an MS2 at a good state school. I would reliably estimate that, overall, I will finish preclinical in the top 20-25% of my class but definitely not anywhere near the top 1-2%. It was a shock and huge adjustment for me...going from scoring 40 on the MCAT and getting straight A+s all through undergrad to only once getting the highest score in the class on a final unit exam in med school. I thought I was a very hard worker, but it turns out I am just a hard worker compared to normal people. I am basically average in that area when pooled with other med students.
I know people with high IQs when I meet them (usually). I have several such people in my family and have interacted with high-IQ people more than most. Also, my dad is a genius and was a child prodigy. While in med school, I have not met many people who I think are like this. IQ-by-profession studies support my observation. However, I know some people who did extremely well in certain classes, and it all comes down to their method of studying and the PRODUCTIVE hours that they put in. Some of them treat it like a 9-5 job and actually study with that schedule. I am envious of them. They exercise, eat healthy foods, keep a consistent and balanced scheduled, etc. Meanwhile I stay up until 4-5am reading random forums and watching YouTube videos.
I typically study a few hours per day, but this waxes and wanes. During one stretch, I never opened a book on the weekend for a solid 3-4 weeks and instead just watched Netflix and stuff. If we have a lot of quizzes in succession, then I will be studying more. Sometimes I study all weekend depending on what we have going on. For me, med school was not difficult academically, but it was a huge social and emotional adjustment period in the first 5 months or so. It made me realize that being "really smart" has little to do with being a good student and having practical life skills like time management and organization.
I see many, many people in my class who go all out with annotating first aid, watching videos, using sketchy something (not sure what it is), pathoma, etc. They could all be geniuses, all be average, or be a mix...I have no idea. But the one thing that all the top students at my school have in common is that they ALL study way more than I do and use tried-and-true review books. I have never used a single one of these resources because I hate looking through books and would rather just look stuff up on NCBI/Medscape/UpToDate.
We have a lot of small group cases at my school, and our unit tests are made from retired board questions. I have managed to consistently score in the low-mid 90s on most of these tests just by doing the small group cases in extreme detail and doing practice questions from UWorld and USMLE-Rx. The catch is that if one of the tests by chance happens to have a lot of random facts on it, then I will end up with a score in the low-mid 80s, while people who spent hours with review books will do much better.
So after thinking about all of this over the past year or so, I've realized that having a lot of IQ-type intelligence is helpful to a point in med school. Taking myself as an example, I can easily recognize the important concepts, Google them, read random articles, and remember everything. For physiology classes a la cardio/pulmonary etc., I barely have to study and can still honor.
The downside is the way that the brain of a person with a high IQ works. Taking myself as an example again, when I study more, I don't memorize more facts; instead, I learn the topic in greater detail and depth, which isn't always helpful in med school when it comes to grades. I also have an extremely difficult time with decontextualized rote memorization, like anatomy in which I did very poorly, because if there is no rhyme or reason, my brain discards it.
And if we were left to our own devices and didn't have small group cases and mandatory review sessions and the like to guide us, I would be totally screwed.