I would always separate female impersonators from drag. I don't think they are very closely related at all.
I always think drag is about something a little complex, which is the way when we are developing we notice and take on certain aethetics that we percieve as signalling that we are attractive to the objects of our desire.
This is more straightforward (not actually, just relatively) for straight people. There are certain socially and biologically driven things - cultural tropes but also just biological sings like breasts or beards - that we see as being attractive to the opposite sex. To some extent we will tend to take these on as part of a self-image, although adults generally understand they are very superficial. But most younger people will make some kind of gesture towards making themselves attractive because it's a very powerful drive.
Or to put it another way, the sex drive is built in and important to most people, but how we navigate it socially is based on a particular set of social constructs that can be somewhat arbitrary. We can't just escape that though, any more than we can escape language if we want to communicate complex ideas.
But for people attracted mainly to the same sex, it can be more complex. Men are typically attracted to cultural signals that are usually associated with women and femininity. Gay men are attracted not just to other gay men, but men who in many cases are attracted to women. I think this is part of the reason why some gay men are somewhat inclined to adopt more effeminate presentation, and similarly some lesbians do the opposite. It's like, which role to you identify most with in a film, the hero, or the object of that person's romantic interest?
I think drag draws somewhat on how gay men understand this element of their sexual expression. But it really doesn't have much to do with real women and isn't meant to.