Tax help for an Irish investor

My take on it is that we have arrangements with certain countries (I am living in Ireland too)
In some cases we might only have to pay 15% but there is alot more variables too this also.

I am still doing my own research and I have not invested yet. I hope someone more knowledgeable can weigh in here. But I do know should be tops 41% or I believe or 20% plus usc prsi if in 1st bracket ect. I would also like to know this even some things I looked up said alot of it can be left to enterpretation, so I am thinking even hiring an expert to just lay this out for myself.