well really you can say that all asians are small. Some of my friends are about my height (and I'm pretty tall).
I think structurally, maybe they are. When I go to try on some clothes, like the other day, a normal medium size wouldn't look as fitting on me as a european brand would.
Then again, my boyfriend always says not to worry too much about what size clothes you fit into- because it varies with each type of clothing.
You are right, weight doesn't matter. Size... it's different for everyone. For your type of body shape and face, you might be fine. As long as you eat healthy and do all that (of course you can eat sweets every now and again ^^") then you should be fine.