How do things spawn?

Game Talk The Bunker
1

Difficult to find reliably up-to-date information on this, and I’d like to get things entirely straight.

Dynamic spawning, afaik, is discontinued and no longer does anything, right?

Static spawning, presumably fairly straightforward - zombies spawned randomly at the start of the game. Number of them proportionate to the spawn rate you set in world generation, and I’m guessing they’re more frequent in built-up areas.
Does the spawn rate affect mobs other than zombies?

Animals - I understand these aren’t affected by the spawn rate, and instead spawn dynamically and randomly throughout the game. How exactly does this work? Do they spawn inside your reality bubble but outside your vision?

Hordes. This is the big one. How exactly do these work? Are extra hordes generated dynamically as you play or are the ones present at the start all you get? Does anything affect how likely they are to spawn or where?
Presumably when your reality bubble collides with a horde, a load of actual zombies get spawned. Does the overmap ‘horde’ then disappear? If it does, can the zombies turn back into a horde after you leave?
Are hordes affected at all by the spawn rate?

And more practically, does making a lot of noise ever actually spawn new things, or will it only attract existing enemies (whether an overmap horde, or actual individual creatures)?

Probably there’s a bunch more questions I’ve forgotten, but I guess this is plenty to start with! Really appreciate any information here!

2

Hordes seem to spawn when there is noise. They spawn at the edge of your reality bubble and seem to despawn if you get close enough for them to be active but not close enough to be seen and then they wander off. Seems like they have amped them up recently but this may just be my own perception. To test this slowly circle around a small town looting what you can from the edges, the massive hordes slowly disperse and you can slowly work your way into the center of town.

I’m sure there is some more intricacy to it than that but noise seems to be the gist of it.

Animals, I’m not sure how they spawn but there does seem to be some dynamic spawning of them as you can see hordes of bats spawn just before night fall, random prey animals popping up occasionally in places that were rather empty.