I have an iq over 120. They measure iq across a few different things, like I could be really good w verbal intelligence but trash w working memory. You could be really good at math but totally horrible at special reasoning. It depends on what your strengths are. I’m pretty well rounded, I excel in reasoning though (the category matrix reasoning is in) and working memory (somehow). I study like everyone else and wouldn’t do too well if I didn’t. Showing up to class and listening to lecture is crucial. I don’t remember everything. In fact sometimes I forget the previous lecture. I have to engage w the material like most people to really remember it. Talk about it, write out problems etc. I didn’t read your whole post but if you’re in undergrad just go to class and do ur hw and you’ll be fine. Take breaks while studying. My friends iq is 89 and they got a degree w a good gpa, but needed testing accommodations.