I think you're over thinking this way too much and putting way to much emphasis on racing category. How do you know what category everyone is? It's not tattooed on most of us. And how much can one know about someone's ability based solely on their racing category or lack of racing category? And how many teams practice team tactics on a group ride? I've rarely seen it.
If the group ride has some organized structure - such as a rotating paceline - then follow the structure. Otherwise, participate however you'd like so long as you are being a safe group rider.