Start and maybe end with Dog Shows.
Take a Camera and attend some local/regional dog shows, if you see a dog you like looks or behavior of after they do round in front of the judge ask handler/owner if you can take a picture of their dog.
In my personal experience not only do they say yes, but they are extremely pleased and flattered.
Those people also make excellent resources for learning more about dogs in general and their breed in particular.
I probably wouldn't mention you are looking for a serious personal protection dog, at least at first, anymore than I'd talk about CCW to random people.
But if you can honestly say you want a dog for companionship and watchdog I don't think that would go wrong.
I've known a couple K9 cops and another guy that trained Personal Protection Dogs, I honestly don't think a PPD is a good option for most people if we are thinking same thing with that phrase. But we might mean different things with that phrase, what I think makes most sense for people is more what I would call a Watchdog, an obedience trained dog that is also trained/encourage to give alert when dog notices people. If you really want effective deterrence 2 or more big or giant dogs trained as watchdog will provide it, without all the negative of a dog trained to attach people.
I strongly recommend book that K9 cop I knew in college via Tae Kwon Doe class, he asked us college guys to help training as aggressors, recommended to me when I asked for resources
https://www.amazon.com/Effective-Aut.../dp/0876055528