Consider an attorney, or a surgeon; consider a country with a 'big boss' attorney, or surgeon, they are called, are they not 'Attorney General' and 'Surgeon General'?

Now suppose we have several countries with these exulted folk, and there is an international convention to which they are all invited.

Is this a conference of Attorneys General and Surgeons General? Or one of Attorney Generals and Surgeon Generals? After all, do we not say 'how many attorneys are there in {name} law firm?' or 'how many surgeons are there in {name} hospital?'?

OOM is to Surgeon General as {X} is to ...?