No they absolutely weren’t. Commonwealth only worked to promote cooperation between member states. It was not like it had any real power over any of the member states.

How would you categorize the status of Canada vis a vis Britain before the Balfour declaration?

No because if they tried, it wouldn’t work. Which makes Canada NOT a vassal state. And it wasn’t not even in theory.

Do you realize that’s exactly what, “For all practical purposes…” means?