No decks are "100% paper". Well, no decks outside extremely cheap novelty decks.
All the decks that we consider "standard" to use in Magic, ie: Cartimundi and USPCC (which are now owned by the same company) are a core of "stock" which is basically glue with thin paper on either side, and then that is covered with a "finish" that is basically textured plastic. I don't know how much variation there is the formulas used for that textured plastic, but some decks definitely feel more slick than others, and of course there's variations of the stock which make the cards feel springier or stiffer.
There's also plastic decks which are, as far as I have ever seen, made of PVC. Some of them have a similar plastic finish as 'paper' cards, which does make them slide over each other a bit better, but you will pretty much always be able to instantly tell the difference between plastic and paper cards.
There's a couple card makers that still varnish their cards, which does definitely feel different than the plastic finish USPCC/Cartimundi use, but if you were buying those you'd know it.