You can read places all over the Internet where people claim to be able to keep guineas and chickens in the same coop.
Most of those posts are by first time guinea keepers. Everything can seem to be going good right up until the first breeding season.
Some people manage to keep both in the same coop if they have an extra big coop and a sufficient number of guineas to satisfy their flock needs. Even those people don't tell the whole truth about the undesired actions of their guineas.
I raised guineas, chickens and turkeys together. I saw first hand how they tormented and harassed the other poultry. I now brood my keets separately, raise and house the guineas in their own coop. I can now let my guineas, turkeys and chickens free range in the same area at the same time without any issues.
You can search this forum and find threads about "Why are my guineas attacking my chickens?" that were posted by the same people that claimed their guineas and chickens got along. The attack threads usually follow the original threads about the time the first breeding season kicks in.
Read the thread
Raising Guinea Fowl 101 and pay particular attention to posts made by
@PeepsCA .