Breed-specific fulfillment for a rez dog?

Hi everyone! I see a lot of talk about breed-specific fulfillment in online spaces about dogs, like playing herding games with your border collie or doing bitework with your malinois. I adopted my boy from a rescue that runs a spay-and-return program for pregnant dogs from Indigenous reservations. The rescue listed him as a German shepherd-border collie mix, but that's just a guess. So I was wondering, what would "breed-specific fulfillment" mean in that context? Should I get his DNA tested to see what breeds he actually is, then learn about different options based on that? Or are rez dogs kind of their own thing, in terms of behaviour and temperament? I live in a big city so I'm not really sure how to recreate the types of stuff rez dogs would usually be doing for him. Or does breed-specific fulfillment not really matter if you don't have a purebred working-line dog? I'm partly looking for fun new activities to do with my dog but I'm also just kind of idly wondering. Thanks!