It would be great if you could do a poll. Though I do suggest that you search prior posts to see if one has been done before.
I currently use a Normcore screen on top. No paper below. I did test it out, with high quality lab paper on top only, on the bottom only and both.
The results are tucked away somewhere, but I did not find any significant benefit to paper below. If my memory serves me correctly, it reduced the body of the shots. As I do like abit of body in my espresso, I stopped using paper below.
As for paper above, it (like a metal puck screen) keeps your machine diffusion screen cleaner and (if I recall correctly) reduces channeling. But I found that a metal puck screen does a better job at that and is reusable. You can buy the screens in various thicknesses, to get the extent of headspace reduction you want and manage thermal loss. I currently use a fairly thick one and preheat it before placing on top of the puck.
As I said I tried the paper out for abit and then stopped.