Looked at 3 of the 4 sites...know one by reputation....
Two are basically American show lines or maybe some combos...little info on breeding stock....nothing that I personally would even look at twice or for your stated needs. One is mostly old German showlines and in house breeding for a few generations with little to no certification - at least hips and elbows are done...but looks like way too many dogs and litters without a serious interest in proving the breeding stock for my taste....
I think you are better off with a companion/lower drive pup from a working line litter if you want athleticism and some performance ability - even a DDR bred dog ....looking over the GSD Nationals entries posted...probably 3/4 of the dogs in the obedience classes were European working line dogs.
Tyson Wittmer has a good reputation and so does Anne Kent of Adler Stein....
Csabre Sch1, Hexe Sch2, Bengal, Komet, Kyra, Kira & Kougar v Wolfstraum ~ Ziberia BH ~ Danger Sch1 RH SAR ~ ATB~ Kougar Sch3, Kyra Sch3, Cito Sch2, Alice Sch1, Kelsey CD, Ret ~ Basha Sch3, Fenja Sch3