You never really know 100% what you’re going to get with a puppy.
We bought a Golden Retriever puppy. He was supposed to become a companion dog for my aged father, and since Goldens are not aggressive, worthless as a watchdog.
Wrong! He has grown up to be a terrific watchdog.
Dad fell and broke his hip a month after we acquired the puppy, and landed in a convalescent home for an extended stay. Meanwhile, puppy is rolling adult Labradors at doggie day care because he was too aggressive with other puppies his own age and size.
At age 8 months this puppy killed and ate a Mallard duck that landed in our backyard. Puppy weighed 60 lbs. at the time, and had become a ferocious watch dog.
He is now 3-1/2 years old, weighs 80 lbs. of solid muscle and is anything but a couch potato. Would probably make a good duck retriever - if I could prevent him from stealing off to eat the duck! Oh, and he is a typical Golden in so far as he loves his family. Just doesn’t trust strangers.
So, if your Great Pyranees/German Shepherd turns out to a lovey, don’t fret.
I wouldn’t say the Golden would be “worthless as watchdog”.
Almost all dogs are good as true watchdogs - they are reasonably territorial and alert people to someone strange coming.
Of course, then there are the exceptions, like my current German Shepherd who couldn’t care less if someone is at the door, usually doesn’t know, and if she does usually goes into hyperdrive trying to get love from them.