1. Most customes are converted from Normal Headgears to Customes
2. Yes, but not all have additional stats, as far as I know the additional stats is only limited to the Auras
3. Auras are from Lotti event or Bonus Points (Donation) while Garment Wings are from GM Boxes (which you can win it from events such as Hot Agit)
4. If you are referring to Auras and Garment Wings, no. There are Headgears from WOE Points, KOE Points, Activity Points, Vote Points and PVP Points and you need to convert them to Customes.