Not 8th edition fluff per se. Models of 8th and earlier editions of Warhammer (they even have their own equivalents of Chaos Dwarfs and Reiksguard Foot Knights, something that WFB last had in 5th edition). That's a meaningful difference. Granted, some models are by their nature rather restrictive in terms of fluff, like a rat with a minigun. Others, not necessarily, though making use of that creative space is something that will only be properly explored when the army books get their full remake. The Hellcannon is a case in point. It was turned into the Hellmaw, which isn't a gun in the first place, but a thing that opens portals from itself to elsewhere, with Chaos Warriors jumping into its mouth and appearing somewhere else, such as inside an enemy fortification. A very fitting thing for an army that is about wrecking face in glorious close combat, and whose members are glory hounds who look for ever-greater opportunities to win more glory to advance on the path to ascension.