Ogres are part of the Orc race.
Dragons have different types of dragons which will have different abilities, as well as drakes (humanoid dragon hybrids) that will serve as resource gatherers and basic foot soldiers. So far the Dragon playstyle is slated to be high cost for high gain, meaning your dragons are going to cost tons of resources to build, but are well worth it.
One thing that I don't believe has been mentioned is that our concept for fog of war is based on line of sight, so if you have a dragon who can fly, they will have a huge line of sight, and give you a great strategic advantage. Also can be said for the other races if you place your scouts on mountains or cliffs, you will get a better vantage point.