Hi Santy,
Browser Library is a wrapper around playwright, so by using Browser Library you are using playwright.
Actually many of the Robot Framework Libraries are wrappers around the underlying tech, this is actually a good thing as you don’t need to learn so many languages, you just need to learn the Robot Framework syntax/approach, but an extra benefit is you can also easily combine tools that wouldn’t normally be easy to combine so by using Robot Framework’s Libraries you can get that extra benefit.
Dave.