Energy and drive are different things. A good sport dog will probably be high drive and maybe low threshold which is not what you are looking for.
You probably need a low to moderate drive dog with a high threshold.
The problem is that many working line breeders will say their dogs can be top sport and also great pets. It is certainly possible but if you wind up with a hyper dog with high prey drive and low threshold you most likely won't be happy.
It's a bit of a jungle out there and I'm not an expert but I would advise you to seek some help off the forum to locate a breeder who has what you want.
Be cautious of recommendations from here or other forums unless you know the person. I say that because I have seen people join this forum who have had there first GSD for about ten minutes and in a month or so become experts in all things GSD. Including breeder recommendations.