1, what feels comfortable for you, is the "right" answer :)

1. yes it does, it is just for "fine tuning"

3, cell = 300 tiles x 300 tiles, 9 cells around you used (mainly) for simulating zombies (outside your "reality bubble")

https://www.reddit.com/r/projectzomboid/comments/plzuef/rough_visualisation_of_cell_size_larger_than_i/

chunk = 10 tiles x 10 tiles, these get loaded, in/out of your bubble as you move around

if you loaded a "chunk" in last 16 hours, it will not respawn a zombie on that chunk

your bubble is as far as you can see panning the camera