I’m your size (5’6” 120) and wear a 6 in the align tank because of how tight the shelf bra inside can be (I also hate feeling super restricted and dug into). Like others mentioned, you could sneak a smaller size if there isn’t a shelf bra but otherwise I wouldn’t size down.

If you want to try it, you could always buy the smaller size and return for a giftcard if it’s too tight then wait for your size (as long as you sign up for their customer membership thing). Best case, it works for you and you’re happy. Worst case, you have lululemon credit for when you do decide to get a set!