@_Vic_ I enjoy how in most of the ()'s you listed the (sub)class names, then for the rangers you listed "(demon and undead)." xD
Fair warning, undead ranger is only a party member if you pursue the Lich mythic path. Every other mythic path either doesn't get an additional party member or gets something entirely different instead.
For example, Azata gets a dragonling that, on top of the usual dragon things, gains access to divine spells that gets stronger throughout the course of the game, along with her dragon breaths eventually having friendly fire removed. It's speculated that she'll eventually grow into a size where your character can mount and ride her into combat too, if you're built for that.