The more you have, the farther they roam. They usually always come home several times a day. However, to few may go looking for others to join up with.
Do they get along with chickens? Mine are raised with other poultry, so they tend to get along (as well as guineas can) with each other. That being said, they become bullies if penned up in close quarters.
Now there is a trick to getting them to stay, and bringing them all inside at night to be locked up. First, when you get them, put them all in a large cage inside where you want them to call home. Two cages side by side if you get a lot. Keep water in with them but only feed in the evening. After a week to 10 days, let ONE out. Put out some water beside the cage and a little feed in the evening like you do the cage. He/she will stay close by and roost there because the rest are there. In a few days, let another one out. They will start to explore the area, but stay close. Keep letting them out one at a time pr day or two till eventually they're all free. Continue the evening feed routine about a half hour or so before dark because that's what they're used to. Then lock them up safely when they enter for their treats as usual. Guineas are creatures of habit, and if that's what they get used to, that's what they'll expect. Brake from the routine and they could start roosting in the trees. That is a very hard thing to stop once they start.