"I heard those breeds are very territorial, and aggressive."
Yes.. and no, let me explain.
Here's a perception. The dog selectively chose to be domesticated by humans approximately 10,000 years ago. I state that they chose, merely because of the way most dogs still inherently keep their natural instincts. Now all dogs are different in their characteristics, some dogs can be hunters, others can be quite timid in nature. At the end of the day, dogs will always have their wild animal side and that is something humans can never fully take out of them. On the contrary, they can be trained.
ARE THEY AGGRESSIVE?
Mine has never really shown aggression. Chow Chows are protective in nature. They are also hunting dogs, so they will run after rabbits. But what dog doesn't. Again, it's about making the puppy's upbringing be relatively amazing. Treat them how a proper dog owner should; give them the right amount of attention, give them the proper amount of nature. For example, like a Husky, the Chow-Chow will just sit outside where it's nice and cool. Remember, the Foo Dog statues you see in front of Chinese Temples are based off these guys. They are more so guard statues then they are dogs. It's just a better outcome for everyone.
Be sure to introduce them to other animals and dogs at an early point in their life so that they are use to that kind of surrounding.
DO THEY SHED ALOT?
Not really, not as much as they look like they would. Their fur does get matted, so it's necessary to brush them often. They only ever shed during the season changes. They actually make good seasonal chrono triggers to let you know when the next season is about to come, almost around 1-2 weeks before. And when it's shedding time, the hair isn't flying all over the place, it generally doesn't take a lot of effort to comb it off either. BIG NOTE: You should NEVER shave a Chow Chow's coat too short. Their fur is is a natural protection from the elements but also does act as a temperature regulator.
DO THEY GET HOT?
Yes. It's not a good idea to have a Chow-Chow in desert weather or places that are generally hot in climate. They are breeds that we're born in the Northern part of China. They are WINTER dogs for sure. They love laying their bodies on cold ground. This means they probably will not sleep in the dog bed that you may have bought them. They will sleep on the hardwood, or on cement or tile, and will move often. Similar to how some humans love cold pillows and will switch it from side to side when it get's uncomfortably too warm.
ARE THEY LAZY?
Kind-of. They can be stubborn. They don't play fetch but they do like to hunt, so they'll run for the ball. They just won't bring it back. They like to just chill most of the time, and when they do play, they can go pretty crazy. But for small time bursts.
It's all in how they are brought up.
Like with all pets, (and almost can be relatable to humans) the environment plays a big role in what character traits they develop.
I've always wanted to befriend a Chow Chow. I never knew at all the stigma behind why owning one might not be a good decision. Even when I met mine to bring him home (little Gohan), he was cool from the start. The more time I spent with him, the more I recognized that everything I ever read online about the Chow-Chow breed makes them out to be 'hard to take care of'. Well, I'm here to break some of the myths. This is coming from somebody who has one.