The PE mod is placing a layer of PE foam between your plate and PCB. It’ll give you a more marbly/poppy sound that some people like. This video shows how to PE foam and tape mod your keyboard. I like the sound of PE foam on my keyboard.

Use painters tape for the tape mod, rather than duct tape or electrical tape. It’s not particularly sticky and won’t leave residue if you want to remove it down the road. I did 3 layers of tape on my Q5. I also put PE mod on my Q5 which is fairly easy to do.