I wouldn’t put too much emphasis on the size of the undergraduate population in general. I would pay more attention to how many engineering students there are. That will have the most impact on how “big” the school feels to you, because it’s what influences how many people will be in the classes you take. I don’t know the breakdown, but GT may be smaller, but still feel bigger.
Your opportunities will be based much more on what you do to distinguish yourself with your GPA, school projects like your senior project, and internships/coops, than they will by which of these schools you choose. Sure opportunities will be different, but you can’t say unequivocally one school’s will be better than another.
The salary you make will be driven far more by where your first job is than where you go to school.
So, those two things given, paying attention to cost actually IS important. Why? because you, your parents, or both, can do something with the differential. It’s called opportunity cost. Over a career it can amount to MILLIONS of dollars. Let’s say for example one school is $100K cheaper than the rest. If you were to invest that in the total stock market for 40 years and get the historical market return, you’d have over $4M! That’s before inflation, but that’s how much MORE money you’d have to make over an entire career to make up for that opportunity cost.
I’m in no way saying choose the cheapest school. I am saying that there is a financial cost to the decision. Given that these schools are generically the same, I wouldn’t discount the price.
As far as the minor in CS goes, minors in general aren’t worth the paper they are printed on. The usually make you take more classes at the expense of depth and breadth in the area you want to concentrate on. Employers don’t care. They care about the competencies you bring to the table. You’ll likely get plenty of plenty of programming to demonstrate that.
Lastly, don’t assume that you will go to graduate school. You don’t even really know yet what engineering is. No one does until they get pretty deep in the weeds in their curriculum. Your interests will evolve as your knowledge grows. Things change. You might get burned out. You might have all the skills and connections you need for your dream job with a BS only. Start with the assumption that you will NOT go to graduate school, but make yourself the best candidate that you can with strong coursework, good GPA and projects. Seek out the opportunity to do research and it will help inform your decision.
Congrats and good luck!