Videos
Go with what the brand recommends or the flooring instructions specify.
Compression of additional underlayment, under normal use dynamic loads (walking etc..), may cause unnecessary movement and flexing at the seams / joints and thus possibly lead to premature failure.
This can result failure of the moisture seal at the seams, or mechanical locking, or cracking of the tile.
For planks with attached underlayment, it is not acceptable to install additional underlayment prior to flooring installation.
Pergo Xtra documentation
The instructions will be painfully clear about this. You really should read them thoroughly to achieve a satisfactory outcome and not void your warranty.
I'm installing either a vinyl or laminate click together floating floor, not sure which one. I am using this quiet walk plus underlayment, i started a room already and was pulling the underlayment a bit tight to reduce wrinkles, as well as stapling it down. Come to find out, instructions say to adhere the laps, but nothing about fastening the underlayment to the subfloor. I did pull the strip and adhere the laps together, but did I make a mistake by stapling the underlayment to the subfloor? Should I not have pulled the underlayment a bit tight? I would appreciate any advice, thank you