As far as I know, the event is mandatory. But it'll probably be over soon.
If you want to appear as your "regular tori", you must be either decapped or receive a neck fracture.
Do I HAVE to participate in this event, like can I be my regular tori, Im tired of being a zombie, vampire, how do I go back to the regular tori
I think all you have to do is Survive from Zombie or Vampires attack, Events will ends when its ends. anyway, you can buy Zombie killer potions if you want, you will be like ordinary tori (you can see your own texture, items etc...) just you used to be a Zombie killer