I've read that monsters tend to reflect specific fears but I'm not sure how much stock to put in that kind of psychoanalysis. Surely some writers just use monsters because it's easier than focusing on a villain character's motives and development when you just wanna make them scary and strong. Ono's not exactly subtle about what she's going for with her vampires.

Yeah, VNs are basically clicking through text with some character sprites, music, sound effects, and sometimes a CG. Many do involve choices to change the routes of the story and voice acting.