Which majors/programs are easier to get into when your applying as a freshman for University of Miami undergrad?

This might get a bit complicated, but in general, the idea that colleges have more selective and less selective majors is actually not all that true. This is a really common strategy, but in most cases it's actually a bad idea.

First, the only time where schools will have a difference in competitiveness between majors is, sometimes, between separate internal colleges (like a College of Business vs. a College of Engineering). If two majors are in the same college—like a biology major vs a history major in a College of Arts & Sciences, there's no point to doing this at all, and (for a reason I'll talk about later) would actually hurt your chances to pick something aside from what you're ultimately aiming for.

If they are separate, like the example you gave, you then have to think about how your individual profile will match up to other students applying into those majors or programs. In the admission process, schools are going to mainly make you compete with other people applying into the same major—if you're, say, interested in business and have a bunch of business ECs and electives (but not much related to writing, media, communication, etc.), you would actually have a better shot of getting into a business program than a communications one at a competitive school. And remember, in addition to that, most schools will make you write an essay about why you want to study the thing you're applying into—it's going to be harder to write a good essay about a program when you're really aiming for another one.

Changing your major between different internal colleges (like going from a School of Communications to a College of Business) is also actually a bit harder than just switching majors inside one college. You'll usually need to do what's called an internal transfer—which is like submitting a whole new application for the major you want to switch into, with a personal statement and recommendation letters from current professors. So it's not guaranteed that you'd be able to switch after freshman year.

The only case in which this is really an advisable strategy to take is when you're split equally between studying two things and one of them may be less competitive than the other—for instance, if you'd be happy and satisfied with the major you initially get into if you were to have to stick with it throughout college. Otherwise, you should just apply into the major you really want, because that's likely what will match up best with your profile and make you the most competitive applicant you can be.

It seems like @jcdenton already gave you a great response. I just want to echo what they said. While the idea may seem appealing, you definitely shouldn't apply as a communications major unless you're OK with actually doing that for 4 years. Continue working on your profile as much as you can over the coming months and apply to U Miami as a business major.