I would call these lounge bras. They aren't really a sport bra, there's not that kind of support. But if you want just a little something, these might be what you would like. They're very stretchy and comfortable. As you can see from below, there isn't a huge difference in band sizes, so the main thing you gain from going up or down is to make the straps a little shorter or longer. There's also not much variance in the pad sizes between the smallest and largest size (see pics).
Band sizes, unstretched:
S/M: 23" - stretches to at least 42"
L/XL: 24" - stretches to at least 42"
1X/2X: 24" - stretches to at least 42"
2X/3X: 28" - stretches to at least 44"