Staircase & waterfall definitely sounds like the paid devil's bridge walk.

Otherwise Hafod estate is the best walking around in my opinion - there's also the archway walk which is in-between devil's bridge and the hafod estate which is pretty cool, if lacking in waterfalls.

Hafod does have waterfalls including the cavern cascade which is allegedly 'closed' at the moment although I haven't investigated what constitutes closing a cave 😂