How does respawn work?

[ViSpace]

Let's say I set the starting zombie pop multiplier at 1.0, set the peak at day 120 with 2.5x pop and turn off respawn. Suppose if I clear out an area before the peak day, will there be zombies spawning there? Also will the zombie population will multiply by 2.5x when it's day 120, or will it increase gradually over 120 days?

[Armagenesis]

If your initial population multiplier is different from your default population multiplier, new zombies will spawn until it reaches the default population.

From what I've seen, at least, new zombies will spawn during peak population day but nothing in between. And they can spawn in a cleared area as long as said area isn't blocked off and they can find pathing there.