I know that malays have three "bumps", and have strawberry combs, but I heard malays are usually taller than shamos and shamos are bulkier that malays. All the pictures I have seen of shamo roosters were usually very scrawny looking, but people say they are 11 pounds and malays are 9 pounds (talking about the roosters) is this true?
Malay or shamo?
It would depend on the line how tall or heavy they are. There are more than one variety of Shamo, the O-Shamo are the big variety. Ga Noi can give them a run for their money in terms of stature, as well as some strains of Thai, but the Thais are usually a little lighter and racier built. There are varieties of Asil that get every bit as big as Malays and many schools of thought consider Malay to be derived from a variety of Asil. Hatchery Malay and Shamo don't really enter into the discussion as they are likely a combination of the two along with goodness knows what else. You are correct in that the proper Malay type calls for three distinct arches in the neck, back and tail, while Shamo are supposed to be more upright and straight backed.
One more thing to consider, in reference to the "scrawny look" you describe, is that these birds are much heavier than they look. Their bones are denser and not hollow, and their feathers are hard and tight to their bodies, you aren't seeing the fluff that you would see in the barnyard breeds. They have a lot of muscle as well. If you could get an Oriental to lay down the fat that some of the other breeds have, it wouldn't be hard to push the known limits of chicken weight, but their gut systems are a little different, and they don't get fat the same way as other breeds. I have seen pictures on another site of a Kulang Asil that was supposed to weigh over 20 pounds. looked as big as a turkey. Probably took him at least four years to get that big, these birds take a long time to reach their full size.