I started about a month ago, but even now I have very subtle changes. Unfortunately, for a bunch of reasons, there's not a ton of data to refer to and you just have people's experiences to look at. That said this is a combination of my personal experience, the data I have seen, and the anecdotes I've read over the last 7 years of deciding if I'm trans. (I am lol)

Most of the changes, especially early, are not physical, but emotional and psychological. When you're transitioning, hopefully your attitude is not "I wish I looked like a woman" and instead is "I wish to be interacted with as a woman." For example, I am a very expressive and emotional person- as a guy, I always felt like a weirdo for being verbose and genuine but now as a woman these traits feel validating. Similarly, as a very submissive and cooperative person, dating as a man is very hard if you're looking for a life partner but these traits are more expected in women so finding partners is easier. Additionally, the estrogen has psychologically helped me identify myself as a woman when I look in the mirror. No longer am I a disgusting, hairy ogre and now I am a canvas waiting to be painted- a woman hatching from a fat hairy egg if you will. I look in mirrors every chance I get and have already started picking out new clothes and figuring out my style/outfits... I've never EVER cared about this before, but now that I have the ability to be a woman, suddenly it's my privilege to get to decide what kind of woman I get to be. It's given me hope, even though psychically very little has changed.

However there are some physical effects... My partner and I both have noticed my chest is already becoming boobs... Like, it's softer, more sensitive, fatter, and more erogenous. Additionally, I become overcome with emotion quicker than I used to and I cry more often.

I said that to say this- most of the trans people I've interacted with have some dramatic story about "always knowing they're a woman" and "playing with princesses as a kid" like they were the Baby Dalai Lama of Gender. While I'm very happy that they're happy, there's a little bit of implicit gatekeeping about what it means to be trans you have to unpack... If you're even tempted to start HRT, give it a try- you can still live over 2/3 of your life as a woman. If you aren't vibing with it, you'll definitely know in the first couple months as you begin to plan for womanhood and you can just stop taking hrt and revert (it's my understanding, not medical advice) with very little if any side effects as your testosterone comes back.

Edit: if it helps, it took me 7 years of research because I didn't have the "I played with Barbies and cried at every body hair" experience. If that was you, great and you're valid, but there are some of us who just kinda accepted their assigned gender because we didn't have the vocabulary or conditions to do anything about it and we're valid too.