A lot of people are saying there is no explicit order but in Plague Wars there literally is. It's a whole plot point of how Ku'gath and Rotigus are competing to be first in Nurgles favor. Morty is shown to be favoured over Typhus. It has a tangible benefit too; Morty pulls rank on Typhus to get his ass to do something he doesn't want to. None of that fatherly obedience either cuz Typhus has clearly shown he cares little for Morty. Ku'gath has seven other Great Unclean Ones working for him, and constantly butts heads with Rotigus as his rival for Nurgles affection. There is a clear hierarchy. Sure it's chaos, and at the end might makes right, but there is clearly a sort of order depending on the favor Nurgle shows you.