I think one of the most interesting things about this fight is; what kind of facial hair is Charr going to sport? A recent picture of him related to this fight had him with the immaculately groomed facial hair of his boxrec profile ... so he's maintained that all this time, probably with daily effort. https://boxrec.com/en/proboxer/314362 He does look a touch perturbed in that pic, possibly from constipation.
You either die a Diamond Boy or you live, long enough to see yourself become a Cubic Zirconium Geezer.
Dubois definitely KO's Charr. Pulev might still have enough left to go 12 rounds with Dubois, even at 42. In his prime he would of beaten Dubois without much difficulty but he looked pretty bad in his last fight so now he'd probably lose to DDD, but he might have enough veteran craftiness to hug and clinch his way to a 12 round loss.