Some dogs are more prone to yap, but I think alot of yapping is lack of socialization and training. I don't own small dogs nor have I ever But the caviliar King Charles Spaniel was apparenty bred specificially to be a lap dog. Plus I think they are adorable. Seems a CKCS was bred for decades specifically for the purpose you are looking for.
Good luck in your search.
Good luck in your search.