Might it be odd for a student to love and have excellent academic performance in all subjects—I am that student. I am really confused what to study in the university. My grades are similar (high) in all subjects, and I prefer both scientific and non-scientific subjects. It's like I want to get a degree in all fields. How can I decide what I should choose? What can I study? I have tried a lot of tests, even paid ones, but I get similar percentages for all choices.
I would pick a major that maximizes your future options. Not necessarily one that will get you a job, but one that gives you a strong foundation so it's easy to pick up knowledge of other subjects.
One good major for this is math. Once you have mathematical sophistication it's a lot easier to learn other fields, like physics, engineering, computer science etc. In general, I think it's a lot easier to switch from math to a more applied field than it would be to switch from an applied field to math. (Personally I majored in math, and then switched to computer science, which is another major I highly endorse.)
Besides, it is a very fun major. At any reputable university the homework assignments require original thought and no two problems are the same.
In terms of career options, most math majors I knew either (1) went for their PhDs (2) became traders/took other jobs in the financial sector (3) branched into software engineering or data science.
Performing well in every subject is simply impossible past the high school level. Conversely, I would argue that a strong high school student in a US-style system should be able to perform acceptably in every subject (excepting effects of disabilities), since studies in high school are typically designed to give the sort of general grounding that will be required in most professional careers (critical thinking, analysis of written ideas, clear exposition of your own thoughts, creative expression, foundational mathematical and scientific knowledge).
Beyond high school, one might still have the potential to be good at any particular thing. It is just that this is the time when one begins to study specialities more deeply, and there are simply too many of them to be an expert in all of them. This happens in a fractal manner at each level: in undergraduate, you can be excellent at whole major, but cannot study all the majors; in graduate school, you can be excellent at a sub-discipline, but cannot study all sub-disciplines; as you establish a career as an academic, it is important to identify a small scope of contributions within the disciplines you work where you can contribute uniquely well.
These realities also imply an answer to your dilemma. You don't have to pick the "right" academic focus, you just have to pick one that you will enjoy. And you can even afford to be wrong a couple of times, as long as you figure it out and shift to something that suits you better. Moreover, it's possible to do this at every level (though it's harder to make large shifts the deeper you go), undergraduate, graduate, postdoctoral, and even beyond.
In short, you can think of academic areas like the Tim Minchin love song says: "If I didn't have you, someone else would do."
It may help your search if you change the question slightly. You have been doing very well in all subjects, and you enjoy them all to some level. So the questions "Am I capable of passing exams in (subject)?" and "Would I enjoy studying (subject)?" are not giving you very informative answers.
Rather, consider asking: "Could I imagine not studying (subject)?" For me, this helped eliminate a few options from consideration when I was choosing school subjects, and has continued to be a useful guide. At the school level, I decided not to continue with studying chemistry - not because I was bad at it, or hated it, but because it didn't grab my interest for further study. Likewise, when applying for university study, I decided not to go for French, because although I like the language and literature, I felt that I didn't need a degree in French in order to satisfy my interests. And so on. On the other hand, the things that I have chosen to pursue are topics that I can't imagine being without.