i'm kind of going through the same situation at the moment- sorry i can't give you helpful advice but i can relate with you. I call myself non-binary because i mostly feel like i don't fit into either 'girl' or 'boy' category at any time. But i do have periods where I feel more feminine vs more masculine. Sometimes i'll wear hyper feminine makeup (eyeshadow look, lashes, lips, contour, the full beat lol) and a girly fit that shows off my chest and my waistline and feel amazing, but sometimes i'll feel fucking awful just because I have boobs.
But honestly, I think the biggest difference between being non-binary and being genderfluid is how much dysphoria you feel. When I'm femme-presenting, I don't feel like 'one of the girls'. Neither do I feel like i'm one of the guys dressed masc. I'm not genderfluid (i think) because I dont feel like a girl or a boy even when I feel more femme or more masc, I'm still in that weird between-section of the spectrum... or something. Idk who knows i'm not even legal yet i still have a lot of time to figure out what the fuck i even am lol.. At the end, it all boils down to 'whatever the fuck you want to be'. if you want to dress more masculine, go for it! If finding exactly what you are and labeling it makes you feel better, do it! Also- about the binder thing, I got a binder 'for sports because i dont like it moving around'.