My original email was a question on luck items and luck cloak.
I asked if I had 66% in luck items and used luck cloak if i would get 100% drop rate.

That was his response.

Is there is a cap only when using luck cloak (which it should not be since the cloaks description explicitly states it works with other items)?

I don't know.

But there seems to be no "luck cap" because some people have bought all possible luck items and that is way over 100%

Again luck cloak description states that luck is directly related to drop rate 100% luck should mean 100% drop rate.