There isn’t one universally “proper” composition for two people standing together. In practice, all of those placements can work.

A good approach is to treat composition rules like the rule of thirds as guidelines, not formulas. If the couple is the only important element, centering them often works well. If there are background elements, lines, light, or scenery that help the image, placing the couple off-center may create a stronger composition by balancing those elements and guiding the viewer’s eye.

The best framing also depends on mood and intent: tighter framing emphasizes connection and expression, while leaving more space can include environment and context. Their size in the frame should be chosen based on what you want the photo to say, not to force their heads onto a specific grid line.

So the key is to compose for the whole image: subjects, background, leading lines, light, and story. Use the “rules” as starting points, then adjust by eye.