Form IDs are used to determine which animation plays for a specific action. For example, ‘walking’ is an action that could have lots of different animations: walking unarmed, walking with sword, walking with bow, walking while injured, etc.
The form is used to help determine which ‘form’ the action will take.
Typically, I set the Actor Core’s Default Form state based on the weapon set that is equipped.
Current values I use include:
TRAVERSAL = 0
COMBAT_MELEE = 100
COMBAT_RANGED = 200
SPELL_CASTING = 300
COMBAT_RIFLE = 500