Create a rectangular boundary for Rect Light

Hello!
I am a beginner and in my scene that I working right now I have a ceiling LED light. I tried to put a Spot Light but it dosen’t make any sense because my ceiling LED of course it is rectangular, and the spot is conical. So i tried with Rect Light because of the rectangular boundary for the light.
The problem is that since it’s attenation radius is spherical and I only want it to light in some spot, my Rect Light actually lights in all directions because of the spherical radius.
How can I make it light in a rectangular form, only in it’s boundaries from the barn angle/height, and not in every direction?
(One thing to mention, I heard that for VR, you must disable Forward Shading in order to work. Is it that true…are therey different settings for Rect Light when it comes to a non VR project and a VR project?

Thank you!