For example, if your major is more/less popular, etc. does that affect your chances of being accepted because of the number of people applying for the same major?
It depends upon the school especially if they admit by major.
That would depend on the school. You might ask admissions. Have seen admitted students’ names drawn random from a jar of qualified students. Lead balloon! So, look for ways of selecting students from a poo! of qualified applicants seeking competitive major. Listing a potential major at application is not a great deal own for the school because students may not select the major or are unqualified. Maybe Admissions knows.
it really depends on you school but a lot of admission officers suggest that you apply to unpopular or new majors
But if you apply to an unpopular major or a new major, you will need to find out how easy it is to change majors into your preferred major. My advice is always apply for your intended major and try the “backdoor” method which could backfire. Find out how your target schools admit first, then figure out if you need to apply as a direct admit or not.
For schools who admit by major, yes it can. As gumbymom posted - don’t try to game the system though because at many schools it’s next to impossible to transfer into the popular majors because they cap the numbers. Do your homework on the individual policies at the schools were you are interested in applying.
Yes, it matters at many schools.
At most liberal arts colleges, it doesn’t matter, but it would look weird if you said you wanted to study, say, physics, when all of your ECs were in the arts and your strongest scores were in English Lit.
Be honest about what you think you want to study, and if you aren’t sure, apply to schools that don’t require you to apply to a certain major.
Thanks everyone. I wasn’t asking it to mean that I was going to try to play around that 
I just wondered because because of the different classes/academic rigor.
For example, a prospective engineer major would probably have a lot of high level math and science courses while I would have more language / history courses for my intended Spanish major.
I was wondering if major would be factored into the acceptance decision since that person would have more rigorous classes than I would, even though I don’t need those higher level math/sciences for my major.
hope that makes sense haha
It doesn’t matter for LACs, but it can make a huge difference at National Universities where being a direct admit as a CS(computer science) major or as a business major tends to be highly competitive.
If you want to apply to selective colleges, it’s helpful to have high levels of rigor across the board. You would not be expected to have taken multivariable calculus or AP Physics C, but AP Statistics or intro calculus would not be unusual for successful candidates.
For example if you are Hispanic and a female and your intended major appears to be math it could make a difference to a lot of schools such as MIT or Harvard
MIT is not going to be more interested in a high achieving Latina majoring in math vs any other major at MIT.
If you say you want to be an engineer, they are going to look for math and science
classes.
If you want to be a spanish major, they will look for high levels of spanish.
A college doesn’t want 90% biology major so they will try to get a variety of majors.
If everyone wants CS, then it may be more competitive to get into than anthropology.
I am female, but I’m not Latina so I don’t have the minority thing going for me haha! I just love Spanish