They have a single flag, for their kingdom (but all the Asrai kingdom are represented). Two different flags, with different top (one for the male units, one for the female units).
Eternal Guards, Glade Guards, and Wildwood rangers have a flag, and also Wardancers and blade singers.
I won't gave flags to Deepwood Scouts or Waywatchers. Stealthy units should not carry a big flag to reveal where they are!
For cavalry, glade riders have a flag, but not Wild riders or Sisters of the Thorn, since it doesn't work well with their animation IMO.
Questing knights now have two flags. The dukedom flag, and a special grail flag
Other knights have two flags. Dukedom flag, share by all the units from this kingdom, and a second flag, randomly selected among a pool of 5 flags, specific to the dukedom and matching the shield heraldry.
Knigths orders have only one flag. Men at arms, Yeomen and Squires also have only the dukedom flag.
Overview of the knights from the different dukedoms, showing 3 knights errants, 3 questing knights, and 3 knights of the realm, with the common flag, and the random flag.