From anecdotal evidence. Little to medium stray dogs are the ones most likely to snap and chase you for whatever reason. Granted, it could just mean that big mean dogs were put down ebcause they actually hurt someone compared to the abandoned dog with a napoleon complex.
My mom and sister have chihuahuas and my grandfather has a shih tzu, they are all super sweet dogs who have ever been aggressive towards anyone. Meanwhile, a family that lives down the street from my grandfather had a golden retriever that had to be put down because it kept attacking kids unprovoked. Sure, some dogs are more predisposed to be aggressive than others but the way they are raised and the environment they live in plays a massive role in how a dog acts.
Little dogs are mean because shitty humans think “aw he’s so itsy bitsy I don’t have to train or discipline him at all!” Totally ignoring that (a) a dog needs maintenance discipline to be emotionally secure, and (b) aggressive little dogs are unhappy little dogs.
The wolf fact was in the documentary to compare the two. When a coyote and wolf breed, the offspring is bigger than a typical coyote and not as afraid of humans as a typical wolf.