...Guineas I like to think of as the police of the bird world. They're always on guard and alert, running about in their own little posse, screeching at any sign of danger. They also seem to be the bravest and most likely to actually attack a predator should the opportunity arise. However, if they get it in their minds that a chicken or other bird is upsetting them, they can become aggressive...
My guineas do a better guard job then the supposed guard dogs.
- Can you/how do you brood/house different poultry types together?
Yes, it can certainly be done. I currently keep my peafowl and guineas together, then all my other chickens are in seperate pens. But, during the day all the chickens and guineas free range together.
I don't let the peafowl and chickens out at the same time though because several of my chickens are slightly agressive towards the poor peas.
The guineas can be bossy sometimes, but the peas have roosts they can use to escape the mafia (that's what I call my guineas

) if need be.
I have a lone Pekin duck as well, but he has a dog cage he sleeps in right outside the coop. He doesn't bother anyone and they don't bother him.
- Which poultry types compliment each other and which should not be mixed, if any?
Personally, I would never want to mix ducks with any other breed (other than geese If i eve got any) due to mess and them having different reproduction ways. I'll leave that at that.
I've kept pigeons and silkies together with no problem. No one got eaten or stepped on

but the pigeons did have a high roost that was very inaccessible to the silkies.
I think with mixing different poultry types, that main thing would be to make sure everyone has room to escape if they need to. If birds are being injured, then certainly separate them and come up with a new housing situation.