Really depends on how stubborn your dog is imo. I have a husky... a very stubborn husky. I doubt this system would work for her. I can just imagine what's going through her mind "It's worth the pain, just run through the pain! Must get squirrel!" If your dog is pretty docile in general (which most pugs are) then shouldn't really be an issue. Though, I don't really like the idea of shock collars in general. The other issue is whether or not you not only want to contain your pets in the yard, but if you don't want other animals wandering into your yard. The fence only works 1 way; if the animal is wearing the collar. So this means other dogs, cats, foxes, whatever can wander into your yard.
Once again though, for a pug... probably not too big of a deal. They are usually derpy and chill