@Rui Luo, the focus of the cut-out should be the face and there should only be 2-3 pixels above the head/hair and below the chin/facial hair. Leaving such a large space for sources as good as these is a waste and not really necessary.

All cuts should include a little bit of collar. At the same time, the ideal cut only contains 2-3 pixels beneath the chin. Since in some sources, the person in the image may have a longer neck than usual, this would be quite difficult to achieve naturally. This video & this post & this post too display a simple technique of how to cut close to the chin and still display a bit of the collar.