[Lemur]

Do such variants usually come in boxes with unique designs? Or do they all have similar boxes?

Swift this is the description of the 500 edition which indicates that it will include everything in the 1000 edition plus extras:
"This exclusive version of Dragonborn, only available at GamingHeads.com, comes with an additional alternate arm that holds a fireball spell that illuminates and pulses like real fire. The collector can exchange the fireball for the short sword depending on preference. Also included is an alternate portrait that shows the Dragonborn with his helmet removed."