I'll give this a shot
1. I think no matter what line of gsd, they are all smart as whips, can learn just about anything. She's, by my estimate around 8 weeks old? Sleeping alot is not unnormal, they play, eat, poop, sleep
As to drives/energy, depends on the dog and the genetics behind them ..It is what it is
2.keep your training sessions short, and do a few daily, end on a good note,,at 8 weeks, they have the attention span of a gnat, so again, not unnormal what you are seeing.> To build a better bond, I hand feed my puppies for the first month, THAT creates good focus,,when you have a good bond, everything else falls into place..
3. Some dogs will pick up the 'bad' as well as 'good' from other dogs in the home . As long as you do one on one time with the puppy, you shouldn't have problems with your existing dog or your puppy becoming 'bonded' to it. As for rough play,,well barring blood, I usually let my older dogs reprimand a puppy for being a pain in the butt to them..Key is to supervise
I have / had a couple thunder phobic dogs/firework/gun phobics,,but I also have had at the same time, other dogs that weren't and were not 'bothered' by the quirks of the other dogs..
Good luck with your puppy, hope I helped some.