Lots of good info here. I wanted to add two things…you say you have a relationship with your neighbor. That’s great.
If you add a LGD on a small area like 5 acres your neighbor is also going to be listening to them bark (whoever wrote that the Pyrenees will settle in then bark for two hours above is exactly right). So consider this before you get one (I think some are better than others? But in many cases barking is part of how they keep predators at bay).
Second please don’t get two puppies at once. There’s something called littermate syndrome and it’s real (ask me how I know!!). And if you want a working LGD buy one from a working farm where you see the parents in action.