I use a Normcore screen on top, the main benefit of which is that I rarely have channeling (proper WDT needles and technique also contributed). And yes, my shower screen is also cleaner.
I also noticed that flow increased, which I adjusted for by grinding finer. I also had to make some adjustments to the Lelit E settings that control the extent of water entering the group head at the beginning of pre-infusion, as the screen takes up puck headroom.
As for paper on the bottom, I did not like the loss of strength and body that came with using paper, especially as this strength is needed in milk drinks. I was using lab (but not food grade) paper but had read the paper chemistry information of both the food grade and lab papers, and was ok with the lab paper. It was Ahlstrom 6010-1250 Qualitative Filter Paper, 2.5 Micron, Medium Flow, Grade 601, 12cm Diameter paper that I cut into 3 paper disks per sheet. It (and a paper disk cutter) are now sitting on a basement shelf.
And… for me… It’s already extra effort/pain to fish the Normcore screen out of the knock box. Adding the extra step of fishing out the paper as well would further increase the effort.