Always start with the lowest rung in the Chain of Command. If they don't know they'll find out, tell you how to find out, or find out themselves... not necessarily in that order.
Your major doesn't dictate branching. You could major in gender studies and end up branching infantry if you wanted to. The only exceptions I can think of are if you plan on further education for select careers (educational delays for nursing, medical school, law school, etc) where it wouldn't make sense for the Army to put you in another branch.Random question- does your major have any affect on branching? I was thinking of switching to something along the lines of sport management because that is something I genuinely have a passion for, even though you'd have to land a cinderella job to have decent pay.