Kravis Disciplined units have a number of advantages. Lower morale penalty when the general dies, less chance to go impetuous, and they're less worried by routing peasant types (anyone who's neither disciplined nor elite )
You can determine if a unit is disciplined by looking at the troop tips. It's inate to some units.
There's also a building ( military academy I think ) that makes all the units produced in that province disciplined. Unfortunately this isn't reflected in the unit descriptions currently.

Ariaman. Scale determines the size at which the sprites are drawn. You don't need to change it for what you want to do, but if you want to make a unit of pygmies, feel free.
Dionysos's description of the samurai flag is correct. The name's just a hold over from Shogun. It's now used to signofy an elite unit