Unless you are coming in with >20 hours of AP credit (at a minimum), you will not complete a double major in 8 semesters, because Tech does not allow you to count classes towards both majors.
Both the international option and research option are good programs, depending on what you hope to get out of them? Foreign service and public health is too broad of a career description to be able to give you much advice on whether these designators would be beneficial to you.
I would suggest you come to Tech open minded, experience your first semester, and explore all your options before you start outlining some super specific course of study leading to some super specific career goal.
It would not take you 16 semesters (unless of course you took an extremely light course load and failed numerous classes...). You do not have to repeat the core requirements. You just have to take an additional 30+ hours in the second major. If you take the recommended number of hours, it would take an additional 2-3 semesters compared to someone getting a single major. In my opinion, that additional time would be much better spent getting a masters. Second majors are not really that beneficial for either employment or graduate school.
Well I don't know what kind of student you are... So I can't say if you're going to die or not taking 19 hours. But just know that average freshman GPA is around 2.5ish. Also it really depends on what kind of classes you are taking in those 19 hours.
Also I know a guy who graduated with AE and EE in 4 years. However, he took like 21 hours for at least 4 semester and took every single summer classes. Not only that he brought in a lot of AP's.
You can take up to 21 hours a semester. If you wish to take more than that you have to go sign a form saying that you realize you could be destroying your personal health and GPA (that is not a joke; you actually have to go sign such a form...). I would not advise anyone to even take 21 hours.
Can you take 19? Since I do not know your academic ability, I cannot answer that question. I can say that most students find the recommended schedules (16-17) very challenging, and that most would never even consider taking a 19 hour semester. This is NOT high school...
If you are among the top few percent (read: amazing study habits and time management skills, 1500+ SAT, all 5's on AP exams, 4.0 taking 10+ APs in high school, etc...), you will likely be fine taking 18 hour semesters, having a decent non-academic life, and keeping a strong GPA. Otherwise, I would stick to 15-17 hour semesters max.
My advice is to limit your first semester to 15 hours and adjust your schedule accordingly after you get a semester under your belt. You will want to have time to be involved, meet people, AND keep up a high GPA. Taking 19 hours your first semester (unless you are truly brilliant and/or have truly superb time management skills) is setting yourself up for academic failure and being miserable. You can always increase your workload later on.
College is not about racing to the end. While it is great that you want to graduate in four years (and this is certainly very achievable), it is unrealistic for almost any student to come in with little to no credit and expect to complete a double major in 8 semesters.
I think it is around 14-15 on average, but it depends on you, so this number shouldn't matter. I second the advice to take ~15 in your first semester, and see if it is too much/too little for you. See what YOU can handle
Yes, I consider double majoring a waste of time that could be better spent getting a graduate degree(espeically consider the number of departments offering joint BS/MS programs or whose MS programs only require one additional year of study).
Minors take between 15-18 additional hours, and certificates take 12 hours. The exception to this is the Technology & Management program (Tech's business minor), which takes 21 hours. If you come in with a couple of AP credits, you should be able to minor and graduate in 4 years without overextending yourself. Otherwise, expect to stay an additional semester.
It means that you are in class for 19 hours each week.
However, labs only count as 1 hour of credit for every three hours of lab, and math recitations count as 1 hour of credit for every 2 hours of recitation. So, a 4 hour math class means that you actually have 5 hours of class each week, and a 4 hour lab science means that you actually have 6 hours of class/lab each week.
It is recommended that one study 2 hours for each hour of class in addition to other homework/preparation for lab/etc... So, you can see how 19 hours can be overwhelming if the courses you are taking are not easy for you....