if you can find a Flintlock with Legend +200% WD that fits your Build, use it. if not, then use Epic +100% WD.
WD% only affects the weapon it is on and increases the damage of BWD, Power, and Item Quality.
ED% only affects weapons of the same Element and can be on any Item. it increases the damage of the weapon(s) after WD% and WD+. basically, if you don’t have WD%, ED% acts like WD% and you lose a lot of damage potential.