Generally they like to lay eggs in nests that also have eggs, since it 'means' that those eggs are safe and haven't been found by a predator. And yes, they likely will lay there if given the chance between there and nest boxes.
Some hens can coparent with others, some can't. It's just luck of the draw when it's the first time they try it, and you just have to watch them during hatching if you're willing to risk letting them try