A soft cup bra is one without underwires, so it would seem making it seamless too would mean no support at all. While some seamless softcup bras are indeed more like bralets and are meant for smaller sizes, modern fabrics and manufacturing techniques offer bras with no wires or seams that still provide lift and support. There are even seamless wireless bras with padding and molding to enhance shape.
Styles include bras with stretch foam cups that are smooth under clothes, molded contour bras, bandeau styles and many more. Some are constructed with side slings or an elastic underband for additional support. You can find almost any shape too, from plunge push-up bras to full-coverage cups to sports bras, nursing bras and camisole-style bras. All of these will have the advantage of a smooth look under your clothing and the comfort of wire-free construction.