My denomination, like many, believes when the body dies, but the soul endures. Without a body, what is the force of the argument that a person is merely the sum of their DNA or chromosomes?
Is it possible God can put a girl's soul into a boy's body, or a boy's soul in what outwardly looks like a girl's body? Does He have such power? Is it possible He has a plan that is not known to mere mortals? Is our following His plan a sin? What mortal has the power to know God's plans absolutely?
I am asked: how do you know you are female? I reply: the same way you know when Christ has come into your heart. You don't explain it in terms of learned scientific argument and results from test tubes. You just know. Same way.
The body is trans, at least in my view, but I consider the brain and mind as functional parts of the body; not the soul. I can really only comment from how I perceive my own condition; but it all seems to boil down to a brain being coded for one set of hormones, and the gonads developing to produce the other set of hormones. The brain CAN function in this environment, but its a disaster; and the gonads can still produce offspring thus is not a source of selection pressure that would ever cause the trait and developmental sequence to disappear. And so is just biology and body.
If one feels that human consciousness is part of the soul; this gets more complicated...
In my view and perhaps the view of people i hang with spiritually, God is both male and female and as we are made in his/her image (out of some brutish looking primates IMHO), then our spirit is both also. In that sense spiritual beings then have all genders at least the way many of us define it. Biological sex is a function of our natural body and gender is a function of what we learn socially and culturally.
This is possibly why i do not feel like a "new person" as many transgender folks do. Some will say that their old self died with transition. While i see the metaphor, I am the same person I have always been. I have simply corrected an issue of conflict between parts of me in the way i am supposed to.