WaterShut and ElecShut should be a toggle for if they START shut off... for like as if you started months after the apocalypse...
Starter kit gives new characters a few extra items in their bag when they spawn... like a weapon, some food, stuff like that
Nutrition enables the new nutrition system (not sure if it's implemented yet though)
The entire block for zombie config is for tweaking zombie mechanics... spawning... hunting... packing... etc... you can get a decent overview of them if you look in the sandbox settings in the zomboid main menu... like if you wanted to start a new sandbox game... look at those settings...
