I've had 3 yorkies in my life, two that passed away a few years back and one current one. My past two, one was barky and one was actually very quiet unless something was off or unusual sounds happen.
My current girl, well, she picked up some habits from my two older jack russells, like barking at activity at the front door, getting excited/barky when family comes home and barks mad at the other two furbutts when they come back in the house after potty (which she learns on her own there :P). And occasionally, she'll bark madly at something that really displeasures her, which believe it or not is not too often (thank goodness, lol). I wouldn't call her yappy, but she's fairly verbal and only really barks a lot under certain circumstances. But even I say she's really demanding a lot of times, either way, hehe
I remember folks telling me yorkies are those "yappy" dogs when I mention yorkies. And in a weird way, I almost feel insulted, especially considering I've had the two for almost half my life. I usually correct them, saying it really depends on the personality of the dog and how you raise them. Same thing with my jack russells, I get the "they are such hyper/crazy dogs" and under certain situations they can be, but since they are kind of fat and lazy (
kind of our fault there, lol) they are actually pretty mellow.
Every dog I've ever had, had very different & unique personalities and granted when I was younger, I didn't appreciate/notice it as much as I did when I was in my teens to now.