I have 2 coops, 2 pens, and 1 chicken run. I have 15 Golden Laced Wyandote pullets that were born in June that aren't quite able to mix with my 11 Rhode Island Reds, 2 Blue Splash Marans, and the Blue Splash Rooster. The whole group of older birds bully them. I left both pens open to the common chicken run and the older hens and rooster just run them around kept them away from their food, water, and coop. They had to hide together under the coop and the hens still got under there and harassed them. So I will wait a little longer for them to mingle. I am hoping the pullets are laying in the next few weeks. Only one of them is a rooster. So that will leave me with 2 roosters and 27 hens and I hope they all give me an egg a day.
I would go for 2 coops if you plan on raising new chicks each year so you can separate them from the older ones. If you are getting them all at the same time you can put them in one pen until you need to build another.