OverlapParams is a new feature that allows integral raycasting, much like Region3, except it is far easier to work with and it was designed for better workflow. “OverlapParams” specifically, is a filter for possibly involved parts. Functions similarly to Raycasts, but with integrals.
Perhaps you should use OverlapParams for area damage as stated in the OP.
As stated by other people, using Region3 is not recommended anymore, instead, the use of the new SpatialQuerry Api (OverlappParams) is. Functions such as worldroot:GetPartsBoundsInBox and worldroot:GetPartsBoundsInRadius replace the need for region3 in part detection.