Hi, Saoirse.
You will see the expression "YMMV" a lot when talking about HRT: Your Mileage May Vary. There is no way to predict what results you will have.
However, it is very common for chest and other body hair to thin out a lot, get finer, and get lighter in colour once you start on E. I never had much to begin with, and now it is all gone except for two or three hairs.
If it doesn't thin out enough, you may need electrolysis to permanently get rid of it. But you likely won't know that until you try it.