Specific cat breeds arn't really aggression prone. The closest you will see to a correlation in hostile behavior are wildcat mixes, like European Lynx crosses or Bengals and Savannahs as they will not be entirely domesticated in their lineage. If we are not talking about wildcat crosses it becomes more difficult to define, but I think subarctic or tundra breeds like the Norwegian Forrest can be seen as more aggressive compared to traditional cats as they do not flag or vocalize like a normal moggy. So you might be too rough or spook them and only find out by the time they have bitten you and drawn blood while at the same time it seemed unpredictable.

Most affectionate is easier to place. Siamese and Exotic Shorthairs are both very affectionate but in different styles of behavior. Siamese are hyper vocal and constantly seek stimulation or interaction while Exotic Shorthairs are basically quiet and gentle velcro lap cats. Think of the loveble, hyper Golden Retriever vs the slow, lumbering but devoted Mastiff sort of deal.