You can look up Yorkie weight chart on google. There should be a lot info there. Most are pretty accurate from 1 week to adult. This is providing that you don't over exercise for too much muscle mass or making him a couch potato to be fat.
As for looks, it's generally your choice as a pet. You want to make sure you look at the parents to have a general idea of how they will look like. Usually they will look like one or the other, or a mix of the parent. Same goes for as personality and smart.
If you are looking for a show dog then I would suggest going to show for a while and getting to know them for a while to see what is a standard quality Yorkie. I'm sure they will always give you a lot more advice and tips on what to look for in example as bone structure, ears, snout, good jaw bite, behavior, etc....