If you use a separate head mesh like metahumans have, you can just check “hidden in game” for the head mesh and also check “hidden shadow.” You wont see the camera clipping through the head, since it is invisible to the camera, but it will still cast a shadow.
With a camera on a spring arm unattached to any socket, you can then lerp between the world location of your head bone and the world location of your spring arm, and the alpha for the lerp will be a slider for how much headbob want.
