Don't major in Engineering unless you are confident in your Math/Physics skills. Good starting measures would be your SAT/ACT Math score and your HS grades in Calculus, preferably AP Calc. Engineering is notoriously difficult. There are stories of Registrars setting up tables outside Calculus classrooms on the day of first semester final exams for students who want or need to change their majors. Even if you do well, your GPA may not reflect that fact when compared to a less demanding major, which in turn will affect your OML ranking and your chances of getting your preferred Branch.
Engineering majors often allow for few free electives, which means that you would have almost no free electives after accounting for Military Science classes. This will preclude the opportunity to get a minor or even pursue other areas of interest. My son went off to Big 10 State U with intentions of a Chem E major. He had three semesters of college calculus and two of chemistry under his belt before he even started. He loved chemistry and could do math in his sleep. It took about 15 minutes for him to realize that he hated the tedium of engineering and that he had little room in his schedule for foreign language and Computer Science classes. After Freshman year he changed his major to Chemistry and thrived.
Don't get me wrong. You wouldn't be the first AROTC cadet with an Engineering degree to commission, but you would be one of the few. Your best bet is to study what you have a passion for and leaving time for staying in great physical shape. The rest will take care of itself.
As you progress you will develop an idea of which branch appeals to you. The usefulness or relevance of your major to your eventual MOS is a whole other discussion. Generally speaking, it won't matter outside of Nursing or Army Corps of Engineers. Therefore, your best bet is to concentrate on your OML in order to get your desired branch where you will spend the following 4-5 years.
My son branched Signal Corps which has nothing to do with Chemistry other than some basic math. It's all about communications networks. He thrived in it because of the computer science and networking classes he was able to take when he dumped the Chem E major. Last spring he successfully completed Special Forces selection and is in the middle of the Q course. There again, there is only the most tangential connection to Chemistry or communications networking to his future (hopefully) role as an SF Captain.
All along the way, I don't think he ever looked more than about 6 mos. in the future. Instead he kept his focus on what was most fun and challenging at the time. The rest will take care of itself. You should do the same.
Best of Luck!