Just like some others here, I have worked for several Vet hospitals, worked in large kennels and trained in large facilities as well as my own business training. I can say I have encountered a LOT of Chows and chow mixes. Probably upwards of 40 of them. I can count on one hand the number of them that were even remotely trustworthy. The rest? I would have euthanized them given the chance. They *can* be wonderful to their owners and rather tolerant of other dogs, even cats -- that they are raised with. However, they aren't the type of dog that naturally looks to you for direction, and they certainly nearly always resent being handled by a anyone other than their person.
They are a dog that gets a knee jerk reaction of a muzzle in most Vet hospitals and kennels I have worked at. Their personalities tend to be more hard wired than the average dog, IMO, so 'training' only does so much for them. I am not saying they are terrible dogs, a lot of people love them. I know of one Chow mix dog that I really liked. He was half German import GSD, 25% Sharpei and 25% Chow. His parentage was confirmed too. He was really a great dog, his brain seemed GSD though, coloring GSD, coat texture a longer version of Sharpei with the head shape of a Chow. He really was a wonderful dog, but...I never had to examine him, or give him shots or handle him outside of his family. Who knows how he would have been...
This isn't a dog that I would get to be a flock or farm guardian.