Mode 1 will fit the face into the red box so that is what you want. If you are talking about non-cutouts then you need to make sure you shoot loose enough so the images will always fill the edge space. If you shoot too tight in camera then you may and up with empty space because mode 1 doesn’t care about that. It always fills the face to the box and the edges end up wherever based on that alignment and scaling.
This page have all videos and also written descriptions for the alignment modes.