I have done stuff with my eyebrows, but my facial hair hasn't been removed yet and I still get maamed no matter what mood I'm in and what I'm wearing. A friend of mine that hadn't seen me since I was 2 months into HRT told me that he could tell instantly that I was transitioning. I believe him because for whatever reason, the subject of transsexuality and drag queens came up quite a bit before I came out. Another friend of mine saw a picture of me from 1 month post HRT (my school ID, which was dangling in front of her face) and said "Wow... you look COMPLETELY different!". In fact, I hadn't started getting maam'd in boy mode consistently until about 3 weeks ago, which was maybe a month or 2 AFTER I had done my eyebrows.
Yeah, a bunch of passability comes in presentation, but don't underestimate hormones. Yeah, they can only go so far, but they do thin the skin, dry it up, and even the tone out. They do put subcutaneous fat in certain places. The do grow boobs. I can totally tell, with me anyways, that the fat on the lower part of my jaw is gone, and the fat on the sides of my face above my lower lip is growing.
Passing does require work, lots of it. Gotta work on your voice, make up, hair, manners. But IDT I'd ever have passed without HRT.