Your bathing suit should be really really tight. And if you are swimming in races there usually isn't any support. swim suits should be tight and smash down your boobs.
The swimsuit is supposed to be able to stretch well over you whole body and there should be bra pads in the swimsuit to prevent guys having a free show at the pool. When you are wearing a swimsuit, it should feel like you're wearing a bra, no tight-er or loose-er then that. (; Lol.
no, yes and a good fit means that you can't lift that straps in your shoulders really high there should only be a couple cm gap and the legs(if you have them) don't fill up with water or it goes down the front and fills up too