Thanks you for the tips.
I would definitely like to try this! But I tried planar reflection with a mirror and I still need to understand well how to place and configure it. When you insert one in your level, by default it is very big and I am not so sure about how big it need to be. I understood that the X and Y axis need to be in similar dimension to the surface that you want to reflect and you need to place it face to face with it, but I am not sure about how far it need to go in the Z axis (set perpendicular to the surface).
Here an image of the mirror in question with the planar reflection selected :
