So I am joining a Wrath of the Righteous game with a Range PC. The party is only just at level 3, so it will be some time before this question really becomes pertinent. As I understand it, the main enemy focus of this AP are Demons, so I picked up Outsiders (evil) as my first Favored Enemy. I chose this one, for some obvious reason, but also so that my highest Favored Enemy bonus will also apply to Devils and Daemons, should the need ever arise. I was wondering though, if for my second Favored Enemy bonus I took Outsider (chaotic) if, as all Demons are labeled specifically as Chaotic Evil Outsiders, the two bonuses would stack, so that against Evil Outsiders, the bonus would be +4, against Chaotic Outsiders, the bonus would be +2, but against Demons, the bonus would be +6. It would make sense to me if it would, as you are using two favored enemy bonuses to specialize against one (two if you count Qlippoths) enemy type.
If a specific creature falls into more than one category of favored enemy, the ranger's bonuses do not stack; he simply uses whichever bonus is higher.
So, no.
I was about to comment that Demon is a subtype too, but turns out while you can choose any humanoid, outsiders are limited to the list, by design. Which means more than a few just cannot be taken.Never realized that.