I think of RCI ships as activity ships. Going to sleep early? Any ship line can go to sleep early depending on the age and preference of pax but that's not what RCI is known for. There's tons of activities, it depends on what you are used to. I sailed the Explorer last Christmas and people talk about ice skating and rock climbing but these 2 features really aren't the huge, most noticeable features of the ship. The most noticeable features of the Voyager class ships is the royal promenade where they have parades and something of a main street/mallish feel to it and is pretty much the center of activity and main meeting space for the ship. This you can't miss but you can certainly miss both the ice skating rink and the rock climbing wall. The Centrum area is RCI.
On the Explorer the ship was anything but mellow. Go on Celebrity or HAL, those are mellow, especially HAL. RCI is a lot more active.