Will the StrangerVille story-based gameplay appear for all save files?

You have to progress the Strangerville storyline pretty further along in order to get "apocalyptic" and after you complete it; you have options to how you want the Strangerville world's weirdness level to be and (I believe) how far the infection spreads.

It's vert self contained and won't interfere with other gameplay. I think ive only seen certain premades act possessed outside of Strangerville once (I dont remember how far along I was on the storyline)? But it was only temporarily.