Increased melee damage question

The forge strike ability says “added melee damage applies at 500% effectiveness”
I know I definitely want all +melee damage to take advantage of that.

My question is does “increased melee melee damage %” increase the + melee damage specifically?

say I have +200 melee physical damage total from items. would 100% increased melee physical damage turn that +200 into +400 and in turn would benefit greatly from forge strike’s +500% damage effectiveness to added melee damage?

or would 100% increased physical damage give me the exact same increase in damage as +100% melee physical damage?

flat and incresed damage are multiplicative with each other.
it works something like this:
flat gets added to the skill, then damage effect is applied, multiplied with all increased modifiers added together, then multiplied with each more modifier.

Yes and no. The order of application would be different but the end result is the same.

200 flat damage gets added to Forged Strike. This will be 1000 flat damage due to 500% damage effectiveness.

That 1000 added damage plus any base damage (melee skills usually have very low base damage) would get increased by the %Inc. damage.