There is no way to individually select an artboard and change its size. When clicking on the name of an artboard, all the content of the artboard will be selected and cannot be removed.

Can't individually select an artboard and change its size??

tank666 May 16, 2022, 7:59am 2

Do you want to resize the frame ignoring the constraints? Hold Cmd/Ctrl and drag the border of the frame.

Change default icon constraints?