The phrase "extra fluff" means something that is unnecessary or excessive. It refers to additional things that are not needed and can be considered as extra or unimportant. Full definition
Not to say that their songs are simple, but playing parts that need to be played and not having a lot of extra fluff that happens a lot in modern music. (relevantmagazine.com)
It doesn't take work to read this, there isn't extra fluff involved. (withfoodandlove.com)
You also might be noticing a little extra fluff to our tree this year? (roomsforrentblog.com)