As far as clothing goes, I think you can ease into dressing masculine if you want, without having to come out of any closet. I'm gender queer/nonbinary and on the very masculine side of things when it comes to the clothes I prefer and I always wore the clothes I like without having to explain my gender to my relatives.

My grandma is very conservative as most people her age are here(and generally it's a more conservative society, for European standards at least) but both my grandma and my mother only think I'm weird and that I don't care about looking conventional.
Thing is, regardless of your orientation or gender identity, the clothes you like are at the end a personal style/preference thing and we only ascribe them to expressing our gender identity because they've been gendered by society. So I just say I like men's style better and that's that. I would try to explain if I thought they'd truly get it but since I don't think they will, I keep it simple.

Oh and have you seen Cate Blanchett? She's a gorgeous, famous, probably straight and cis woman and often wears androgynous clothes, always had. In fact she probably wears suits more than dresses and some are very androgynous. My point is, even straight, cis women can have a liking for the "masculine" style of clothing and in fact I think a lot of straight, cis women don't consider it as an option precisely cause they know there'd be some stigma or they'd stop being attractive to men. So my advice would be to just dress and act however you like and just not label it if you don't want to.

As for orientation...well, I'm in a similar pickle because I've just really embraced/realised my bisexuality but I can't bring myself to tell anyone in my circle, let alone my mom or grandma. Well, my mom is fairly open minded and pro lgbt rights but she still has a bias and would not be very happy about it. Again, I don't think you need to come out in order to explore your sexuality because let's be real it's not like you want your grandparents to be in the know about your sexual experiences anyway. So I think until u get into a serious relationship, there's no real need to tell anyone if you don't feel safe to do it.