(And for an RPG that I would totally
look into if I was doing this campaign, but that I haven't read or played so I can't speak to its actual effectiveness or ability to be reskinned for medium-magic, is
Mutant Year Zero. Definitely the post-disaster, lots of discovery, and great community-centric mechanics apparently, as well as inter-character conflict support. But all I know is I've heard good things about it.)