Rounded rectangles are easy to manufacture, but ugly due to their tangency. For best results, you want to smooth the curvature—whether in the form of squircles,

Rounded rectangles are easy to manufacture, but ugly due to their tangency. For best results, you want to smooth the curvature—whether in the form of squircles, or something a bit more locally-constrained. https://99percentinvisible.org/article/circling-square-designing-squircles-instead-rounded-rectangles/ https://99percentinvisible.org/article/circling-square-desig... shows the difference nicely if you (or any other reader) are unfamiliar with it.