As mentioned much earlier, "low key" is a product of the individual dog and the training it has received. It also has different connotations and meanings to each individual so is relatively meaningless in a group discussion- especially among mostly strangers.
"Low key" is often confused with "good manners" as an obedient dog is generally thought of as being calm. A poorly trained Basset hound can be just as much of a problem as a Greyhound though often in different ways. It is what the owner wishes to put up with that often determines whether the dog is low/high key rather than actual temperament.
Pick a dog, be firm and consistent on obedience and odds are you will end up with a "low key" dog. If lax in either and a dog will soon take you over whether a toy poodle or a St Bernard.
