Though they weren't my dogs, I did live with three German Shepards for a couple years and they all had fairly different personalities.
One was very shy and timid, didn't have much training, and was often bullied by the other two. She also had some challenges when being around other dogs, so walks had to be with her alone, rather than all three.
The oldest was very well-trained (in German) but didn't really have the training reinforced regularly — still extremely well behaved and would be chill if the other two were outside or somewhere else in the house, and was the best on walks, great around people and other dogs, all of that. Was very easy to loose-leash walk, rarely pulled except if the youngest was yapping at something.
The youngest was kind of a pain, he hadn't been given much training, was enormous, had some separation anxiety, and barked at everything and everyone. Fought a lot with the oldest, some of it was puppy energy but some of it was trying for the top spot in the pecking order. He was so big and so strong even as a 1 year old, walking him was like putting a leash on a motorcycle. He'd be okay with the oldest, but if walked with the youngest, he'd be bullying her or charging at imaginary squirrels or actual people.
They could all get a bit destructive if they were left alone (though the oldest would do fine if it was only him), especially the youngest, though the timid one was a shoe destroyer when she was feeling ignored. They would spend the day in the dog run outside unless I was around during the day to walk them or play with them, so they had a lot of pent up energy in the evenings.
I do love the personalities that GSDs tend to have, but agree that they need stuff to do (and consistently reinforced training) or they will turn their boredom into tearing things apart (these three managed to destroy a couch one day, definitely a team effort!).
