For me it's tighter than a sports bra, unfortunately!

If you have the means, I definitely suggest getting one your size and another one that's one size bigger (e.g., getting one L and one XL). That way, you have an option depending what you want to do that day and wear the one that's more appropriate for the day. For example, I use my size when I'm just going out to the mall or for a walk, but I use the bigger one when I'm going to a crowded concert or doing some light exercise.

I've been wearing g2bc's on/off for about 7 years, and (unfortunately for me, haha) it does not alter the shape of my chest/body at all.