For a two player game, one chem station, 2-3 cement mixer, 3 forges, 3 workbenches, 3 campfires. But that is mostly just "because" and we usually aren't using all of them. And 2 dew collectors with all mods installed.
Single player, I'll only have one of each. I might still do 3 campfires, but only because I separate food/drink items into 3 crates under the campfires, so it is just for looks. And 1 dew collector with all mods installed.
Screamers aren't really a big deal. Perhaps annoying, but that is all. I'll just drop a turret on each corner and ignore them unless I feel like some experience.