Yes, the V-wire underwire is built into the top and holds its position during activity. The wide adjustable straps help keep the fit secure and prevent the top from shifting.
The waistband sits 2.4" at the front and provides 3.3" of coverage at the back. The shorts are fitted through the thigh with a built-in brief lining, so nothing shifts when you move and no separate liner is needed.
Yes. The straps adjust using square slider hardware at the back, so you can set the length to suit your torso and get the right fit through the bust.
The ruching is horizontal shirring built into the fabric across the midsection of the top. It creates a smooth, gathered effect and is not a separate insert.
The set is sold as one size across both pieces. The fit is generally true to size. If you are between sizes or tend to carry more through the thighs, sizing up will give you more room through the shorts without significantly affecting the top.