If you do past life meditation in a proper way, you always incarnate as the same sex. When your soul opens up and you gain more intuitive knowledge of past lives directly, you know you incarnate as the same sex and race. It is not possible to be anything other than what you are. DNA expression and the soul work in tandem.
Transgenders either have tendencies to be more like the opposite sex in their mental and lifestyle expression throughout their lifetimes which is a choice they can choose to live out on the physical side or (way more common these days) they are influenced by current stimuli to want to be something else for xyz factors.
Many trans nowadays would not have been trans before as this is a cultural epidemic at this point that fulfills certain 'needs'. When one looks at 'true blue' trans who would represent as the other sex in past lives, there are many, many complex reasons in past incarnations that this can occur and why someone chooses to live this way, but none of these involve literally being the opposite sex or even being intersex. Even that childhood trans kike of the TLC show brought back to a prior incarnation by a trance therapist said they were a homosexual BOY.
Other than the repression factor of such an individual, gays dont have anything to really do with this.