The size of the poop depends on several factors
Probably the dog that takes the biggest poop is the Great Dane: its stool is estimated to weigh about 500-700 gr. The St. Bernard, however, beats it in frequency and quantity: in a year it poops much more often, about 180 kg more.
Exactly as it happens to humans, the volume of dog poop depends on the size (and therefore on the race), metabolism, health and above all on diet: just think that the food requirements of a Great Dane (about 1,200-1,500 gr/day), or of a St. Bernard (900-1,200 gr/day), corresponds to those of an adult person, and is not comparable to that of the tiny Chihuahua (40-70 gr/day).
According to some, the more the food given to the dogs is industrial rather than homemade (e.g. rice, vegetables, meat), the greater the volume of poop, and therefore increases the work of their owners who, armed with a bag, are rightly obliged to scoop poop from the sidewalks.
A gesture to be repeated during walks with Fido (who does it at least once a day), and which in many cases is equivalent to a big effort. But you know, for their four-legged friends, the owners do this and more.