I have had a few flocks of Guinea Fowl. I have noticed that if Guinea Fowl are raised together with the Chicken flock from youngsters there will be real problems later on. I think this is because the Guinea Fowl grow up thinking they are the same kind of bird as the chickens and part of the flock pecking order. So when mating season comes they will try to mate, fight, display to the chickens.. but these birds have different natural behaviors to chickens so that leads to confusion, fighting and injury in the end.. and a lot of stressed out beat up chickens.
When the rooster tries to protect the hens, the Guinea Fowl then gang up and attack him as they see him as challenging them for mating rights or threatening them... and roosters behavior means they keep fighting... so there will be a blood bath!!!
However, when I raise my Guinea Fowl on their own.. to young adult stage, then introduce them to the chicken flock I never have any problems. The Guinea Fowl will understand the chickens are a different kind of bird to them... so will not be interested in mating with them and hanging out with them, interacting with them so closely.
In fact, the GF pretty much will ignore the chickens then... but still hang around with them when free ranging for protection in numbers and to help find food. They will also protect the chickens accidently.. because if any threat comes near them the GF will attack it to drive it out of their territory, or sound the alarm, to warn the chickens.
These are my experiences... I don't know if others have found the same.