As the other comment said - only cosmetics (and eventual battlepass, BUT Blizzard has said the battlepass rewards wouldn’t be pay 2 win).
I have yet to see a cosmetic outfit in-game. The armour you get from drops looks awesome as hell… You can dismantle fodder gear and they unlock free cosmetic overrides (which you can set as a transmog, and toggle on/off from work inventory whenever).
Oldschool Runescape