Simple fact of the matter is some references were just name drops. Brauner and Olrox are name drops. Their characters resemble Van Helsing's Dracula and Blood: The Last Vampire's chiropterans. SOTN's Olrox and POR's Brauner were both knockoffs of Nosferatu's Count Orlok.
Werewolves and vampires have been around together before Castlevania. Both werewolves and vampires share the shape-shifter lore (Dracula was either a full-fledged werewolf or a more generalized lycanthrope) and was a popular belief in Hungary. Both werewolves and vampires are cannibalistic. Both have been accused by the Catholic Church of abhorring God and cured/defeated by religion (ha! Catholics always try to steal ancient lore for themselves). At one point it was believed that a werewolf would become a vampire if its corpse wasn't cremated. H.P. Lovecraft's "The Hound" was basically an 18th century European vampiric lycanthrope. And heroic werewolves (now referring to N64 Cornell and Van Helsing) were a feature of the Turks, who revered lycanthropic shamans.
What irks me though is, why does Satan always have to appear where there are demons? Let's not get into the fact that "satan" is a common noun, not a proper noun. And bringing Cthulhu (and whatever that thing was Brauner summoned from his painting) into the series, that kinda chucks God and Satan and all that out the window (you can argue Cthulhu was God's creation, but you are only kidding yourself). So instead, for LoS we get this Christianized D&D mish-mash. Satan never appeared in Castlevania, so why now?
By the way, I haven't played LoS so I gotta leave this post on an interrupted thought and leave this sentence unfinished because my girl wants to play a game and I forgot what I was going to ...