Ugh, to go through this as a teenager must be exceptionally hard. My teenage years were filled with denial, so I'm not sure if I am qualified to give advice on what trying to for lack of better phrasing 'come out' as a teen would be like. (I say for lack of better phrasing, because its not necessarily that you want to come out, but just more of... know who you are and be okay with it. Then maybe later come out... If I'm wrong, I do apologize)
So far, you've been privately experimenting with your gender expression. And having a more feminine gender expression pleases you. That in and of itself is telling to me. Especially as you say you can see yourself as a female when you express as feminine. To me, the difference between just crossdressing and being transgender is how it makes you feel and how you see yourself when you change your gender expression.
From here, I feel the need to point out the fact that gender is a spectrum. There will always be people who argue that gender is binary, but they are so way off the mark its sad. Even when I was growing up, people subconsciously recognized that gender is non-binary in giving kids names like, 'Tomboy' or 'Sissy' (though the latter especially is commonly viewed as offensive). Granted these were often viewed with disgust because people believe your expression should match the sex you were assigned at birth. Today they are still viewed with disgust or you're assumed to be gay or lesbian.
The part about being masculine, and liking the parts of you that are masculine, suggests that you fall somewhere in the 'grey area' of the spectrum. The part of the spectrum that's neither male or female, or both, or leaning more in one direction. This is non-binary. There are many different non-binary labels you can adopt, but I just like the broad labels of non-binary myself, which by the way, does make you transgender too. Some people may say you're not if you're non-binary. BUUUUT the definition of transgender basically is, your gender and sex don't necessarily match up.
SOOO my advice, and this will be difficult, as you're not 'out' yet, is to continue changing your physical gender expression. But maybe start trying out different pronouns, and see if any make you feel better about yourself. The best way to do this, at least for me personally, I've found is to explore through writing. Or even gaming. Assign characters to yourself that are female, male, non-binary, etc... And see which one you relate more too... And aaaaaack cutting myself off cause kid's getting into stuff again.
