I'm sure it depends on the strain and the individual bird. The two Ameraucanas I have are the friendliest birds in my flock... it's almost unreal how friendly they are. The breeder who shipped me eggs said he bred for temperament in addition to other qualities, and it's obvious he wasn't a-kiddin'. Even as little chicks, they were the two that would flitter to the top of my brooder when I listed the lid and wait to be stroked and given treats and clucked at.
To be honest, this really sort of surprised me, because I'd been under the impression that smaller birds (Ameraucanas are small-ish compared to my SFs... at 19 weeks they're about the same size as my 12 week old speckled sussex) were flightier and more skittish. Well... they FLY more, but they fly straight to me, and perch on my arm or shoulder and want to ride around while I do my chicken chores. That's one of my girls, Lily, a wheaten Ameraucana perched on my shoulder in my avatar.
I didn't start out by giving them any extra attention as chicks, but they demanded it just by their friendly, forward nature. I've never seen them pick on the other girls, even the SFs, which as a breed can tend to get bullied. However, I don't really give them very many treats because I want to make sure their diet stays balanced, and they get to range on quite a bit of land, so I think they can balance their diets pretty well. When I do give treats, it usually consists of sunflower hearts or scrambled egg or mealworms. I don't give table scraps like spaghetti (even though I'm tempted sometimes!)
Sometimes birds that pick do so because they don't have a good diet. (But sometimes birds that pick are just mean!)