Requesting improvements about planar reflections (4.12)

Please correct me if I have anything wrong. To enable planar reflections in 4.12:
-Enable global clipping plane found within: project settings > rendering > optimizations “Support global clip plane for Planar Reflections”
-Setup a simple material using Roughness = 0 / Metallic = 1.0 / Base Color = 1.0
-Apply material to a quad mesh (mirror)

Play the game and the quad mesh will now have planar reflections applied.

So what is the purpose of the “Planar Reflection” actor found within the “Modes” menu? If I drag this into the viewport, I get planar reflections on this mesh, but only in preview mode and not in the runtime game mode. This sent me down a bit of a path questioning how to get planar reflections actually working.

Just making sure I understand the basics here.

Thanks in advance,