Question from someone avoiding DLC spoilers

I know the DLC draw is focused on the new area you can access after beating Radahn and Mohg.

But I wanted to ask, does owning the DLC add anything to the game before accessing this new area? Would there be a reason for me to own the DLC before I finish getting Radahn and Mohg?

For example, I know the DLC has new weapon types, can they only be accessed in the new area as well?