Is there a way to get all players in a certain area, and access these players in Verse? For example all players inside a barrier device?

You can use a mutator zone, size it to the area that you want then in Verse Subscribe to the OnPlayerEnteringZone and OnPlayerExitingZone to update an array of Player Agents in the area. Then when you want to effect all the players in the zone, iterate over the array of Player Agents.