Braixen and Delphox, while resembling witches, are more likely based on the broader subject of spellcasters. They both use sticks as "wands" and have fur that resembles robes. Their delicate frames and feminine faces are indicative of witches, however, "wand and robes" could apply to almost any magic-wielder like wizards, mages and warlocks. So, in a way, Braixen does resemble a witch. However, it's original concept is more general; a wand-waving magician.
EDIT: I just remembered that in Pokkén Tournament, Braixen rides her wand like a broomstick. This is a trait found primarily in witches. So, I think it is safe to say that Braixen is based more heavily on a witch, whereas Delphox is based on magicians in general (it's name even refers to the Delphic oracle).