Having friends who are indeed "unpassable" trans women, basically here's the deal...
Whether you "pass" or not, eventually you finish the "transition" process. You reach a point where you realize that this is as feminine as you're going to get, you establish this new "normal," and you go on with life accepting what you have and don't have.
Basically if you don't "pass," after a while you get used to the stares, used to having a "queer" appearance, or voice, or whatever it is that outs you as trans, and you just stop thinking about it because it becomes normal. Basically, you realize that you're doing the best you can with what you have to work with. And you realize that the problem isn't with you for not living up to some sort of fabricated ideal, the problem is with the society that perpetuates those ideals in the first place. You're just doing what makes you happy. And those who have a problem with it are the ones who are in the wrong.
So yeah... that's basically what most of my "unpassable" MtF friends say. They realize that they have a right to be happy in spite of not living up to societal "ideals." And when worst comes to worst, they keep a carry letter with them so that they can prove that they really are legally allowed in female spaces, which eases a lot of the worry.
Over time, whatever state you end up in permanently, your brain will adjust to whatever that new default "normal" is, and you'll quit consciously thinking about it. The brain is funny like that.