I've not met many so i'm not sure how good they are with snarkiness, but how about Basenjis?
Basenjis have strong snarky tendencies and certainly are not a breed traditionally considered willing to work with their owner.
What about Entlebuchers? I know you said it had to fit exactly and they are a bit heavier than your preference. Weight can be misleading though, as these dogs are the same height range as many others mentioned, such as whippets - 16-20". They are described as "cheerful", tend to get along well with other dogs, very devoted to their people, very strudy and love to work with their people. I have been totally impressed with what I have seen with this breed in agility.
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