Well, I'm seeing something different here.
Dragons must be raised, taken care of, and controlled by the thinner and shorter riders that you have. You must have, so, someone that is, at the same time:
- Not heavily muscled.
- Shorter than the regular male, on average.
- Lighter than the muscle-bound regular warrior-type.
- Apt to take on nurturing roles, taking care of the dragon-babies since they hatch and nurture them to become fierce warriors.
You need no bulky male. You need some dragon-riding girls!
What I see is a world with far more equality between the sexes. While on non-dragon riding countries the major advantage of the troops is the raw muscle power of the regular army man, the dragon-riding people would experience something new - the people best suited to ride those giant beasts are actually women.
This won't change architecture much, but it will probably put the ladies on a more important scenario - depending on how long this dragon-riding thing is going on, your would could even be a matriarchy, ruled by the ones that can handle the most powerful weapons of war.
I don't see any of this changing the aesthetics of anything, however. Architecture is (mostly) gender-neutral, and if it would change to something different, it would be something more dragon-themed to reflect the iconic beasts of this people.
What is "manly" wouldn't change. What would change is how important being "manly" is to this people. Probably they wouldn't see "being manly" as something even related to gender, anymore. Since there are guys and girls on the army, the standard gender roles are throw by the window and people just stop caring what you do anymore. This is more-or-less what's happening on the world today - with the help of technology, we are each year less dependent on the natural raw power of the males and females, once trapped on less muscle-intense jobs, are now basically everywhere, even in the army. The reflect of this is that people are more and more less concerned to fit stereotypes and more concerned in being happy.
So, the way to go is equality between sexes, if not a bit of favouritism to females.