What raises the power of a move more: elemental plates or type specific items?

Question

Such as which increases the power of a move more: charcoal or a flame plate, magnet or electric plate, black glasses or dark plate, etc.

I know that type specific items raise the power of a move by 20% but how much will the plates increase the power?

Answer 1

They are the same. They both raise a move's power by 20%.

Comments

Why is it so vague about how much the plates raise the power by?