How does voice therapy work exactly?

I know for male to female transgenders, voice is a key factor in transitioning.

So I've heard that vocal training/therapy is necessary to get a decent natural female voice. I've heard that they help you with your voice on certain topics like speaking, tone, pitch, coughing, sneezing, yawning, breathing, etc.

But how exactly effective is it?

Can you please go into detail on how they teach you?

Do they go over other topics like singing, screaming, sounds of being in pain, etc?

And when I start taking estrogen, will my voice "stay" or "remain" exactly how it is now? Meaning it won't get any deeper?

I know taking estrogen won't effect the voice by raising pitch or anything but I just wanted to know more. Thanks for reading! :)