I was never very hairy on my body, but the difference with HRT was very noticeable after about a year. I still have a little bit of hair on my legs, especially my shins, but it is not nearly as much as I used to, and not enough to be worth shaving. Lots of cis women have hairier legs than me. On my forearms, I have a little bit of peach fuzz that is only noticeable in particular light. If I see a longer one catching the light, I'll take a razor to it. I never had any back hair that I know of. All my chest hair is gone except for about half a dozen thin fair hairs around my areolae.
As always, YMMV. Since you are starting out with more than me, it is likely that you will end up with more than me. But it is highly likely that you will see quite a reduction.