How to choose a balanced GSD ?

I am starting my research to look for a puppy. I am interested in a working-line GSD, that I know they can provide security and at the same time they can be a good companion to the family. What I am looking for a security / watch dog that can provide projection when I go hiking , camping or at home. A home companion the family ( My wife and I , and hopefully down the line the kids ), I am also willing to go through trainings and to train her ( I want a female pup).My wife and I work from home.

Questions :

• What questions to ask the breeder about foundational work in early stage ?
• What characteristic I should focus on when choosing my pup ?
• Are there some tests I can see if that dog fits the characteristics ?
• Any tips or advice or things that I should look for or hold it in my mind ?

What I am looking for :

From my limited experience and research that I conducted I came up with the following temperant / characteristics :

• Confident / independent
• Intelligent
• Medium drive
• Stability
• not environmentally sensitive, kind of cautious/nervous/squirrelly
• Food motivation

From what I understood also that foundational training in working line is also important to prepare the puppy for this kind of mix.

Thank you for your help and insight !