My chickens & guineas were all brought here as 3-7 day olds, so they were caged next to each other in my barn for about 3 weeks. Then I moved them to outside pens with their cages as the "coop" until they were about 3 months old. They were then put into their respective coops/sheds which were adjacent to the smaller pens. Those smaller pens are saved for other young stock, hen w/chicks, isolation -- being 4X8 and having made 3 of them, I can connect as needed. I had to buy material and make them, so wanted to be able to reuse!
Anyway, these birds prefer to have their "own" areas for the most part. The guinea are not penned and so are up at daybreak and begin their range work. The hens are released from their coop early each morning (although coop is large enough to keep in then if need be) and they can free range. I find the guineas like to chase the chickens if they are by the coop area at first of day, otherwise they flock with their own and move without too much issue until evening when it is feed and coop time. Ahhhhh, food rules!
I have learned when/where to scatter their evening treats to keep most aggression at bay......if any it has been minor. So, if owner prepared and animals "managed" they are tolerant of one another and learn when/where to roam. With breeding and nesting, the males are a lot more territorial but, we all adjust. In an adjacent field I have 4 mini mares who are 28-31 y/o and while they were friends w/guineas before, nesting has now make the males chase these gals away from the fence on that side. LOL funny to see them running from those "charging" birds. But, a little exercise is good!
Anyone with both chickens and guineas who finds they need to retrain one flock, know that the chickens are easier to work this with............the guineas have a different mindset which doesn't include a lot of flexibility if it wasn't THEIR idea. This is my first year with guineas but I am pretty animal observant and this became very clear, very fast! Reading expert posts here alerted me before getting them but, boy were they ever correct. Believe it.