I know I don't and will never pass 100% of the time, despite many years on HRT and 'the works" with Dr. O back in 1999.
That is simply because of my build. That likely would not have been an issue 30+ years agom but too many people are aware of us and know what to look for these days.
That said even before FFS, after about 8 months on HRT (about 1997-98) , while presenting as male, I was almost always taken as female by wait staff, was smiled at by strange women on the street, and it was not uncommon that when men saw me in the restroom they wondered if they were in the right restroom.
Back then, I got read read as male more when I was presenting female (and i did not dress very fem or inappropriately, just unambiguously female) ...
Basically What that said to me was people have certain expectations for certain body types... and if you meet them, that can take a you a long way. (Of course in the long run it helps if those expectations come close to matching who you are...)
These days I don't get read much at all... but still do occasionally (most 60+women don't get a lot of attention)
I know i do pass reasonably well. I had a nurse practitioner do a PAP smear on me without suspecting I was postOp (Gyn told me how surprised the nurse was when she told her I was TS).
Relatively recently I went to new Endo in a major medical center here. Because of records mixup I had to spend like a half hour dealing with front desk people. Apparently the endo had only dealt with TSes that were early on... she was obviously surprised by how well she thought I passed and said that no one there had a clue... And asked me if I was partnered with or dating a man. (As I said I don't think she has seen many TSes that passed well)
That said, sometimes (though very, very rarely), I still (particularly from those who see me initially from behind) obviously get read by strangers on the street.
The combination of big hands, big feet, broad shoulders, barrel chest and no hips to speak of can't always be overcome.
Basically if one has a reasonable body, all else can be overcome IMO. That said, I have only met a very few in person (so experienced the whole gestalt ) over the years, that I thought did pass 100%.