The questions that you ask can only be answered by you. Choosing a field is very personal. I don't know what nationality you are or what your background is, so do not know if career tools are available to you, but in the States, there are many ways to help sort out what you should try first.
You may have heard of the Meyers Briggs test. This helps you identify your character traits and how you see the world. If you are interested, I am sure you can pick up a book on it. There are other tools that help identify what you are good at, versus what you like to do. They are not always the same. Interestingly, your scores change over time as you grow and develop new preferences.
As for where to get a degree, as you rightly point out, that is dependent on a lot of things such as money, affinity for the country and others. You have to follow your instincts on that. Note that there is a global shortage of competent engineers and scientists. Although competition is fierce, many of my colleagues bemoan the fact that the breadth and depth of knowledge possessed by recent graduates seems to be slipping. The key is to make sure that you get a good education, regardless of where, and that you learn critical thinking. It would also be helpful if you have strong communication skills.
The bottom line is to look inside, versus outside. You will get 100 different opinions from 100 different people, but only you know your self and what you like and dislike. Use that as your guide on where to go next. And if you don't like it, you can always change.