Long post LOL... Long answer... first of all Welcome To BYC... belated but
From San Diego High desert.
Each situation is different Climate Predeators Availability of materials...
Both Chickens and Guineas are rodent getters... Where you see one mousie guaranteed there are five or ten more...
Twenty is a good number... Ten is the bare minimum I would go with... Guineas are not as domesticated as chickens... They have many of their original behaviors and qualities... Dont expect them to act like chickens. their wild qualities get them into trouble so having spares is an excellent idea.
they run along the perches chasing each other... Funner than heck to watch... I use Two by fours hung by v shaped bailing twine supports from the ceiling.. Yep they wiggle Dont seem to bother them... I put my chickens up at about five feet on solid non moving perches So they can get some exercise moving about the coop ... INtermediate perches Help the chickens get up. But Only a few use em to get down.
I set the Guinea perches at six feet and they shoot straight up... during their gymnastics...
Roosting in the cow barn is a great idea.... Poo can be handled by hanging catchers under the perches... Made of canvas or feed bags ... Id put em above the cows heads high enough so the cows cant mess with em...
Poop hammock can be made any way that is convenient... I have an unique setup for my coop The one below is much like I want to do for my own. Feed bags over closet dowls PVC wont work eventuallly bends.
the birds wont walk in them
hammocks are removable for dumping in the compost.
The concentrated pooping happens at night.
I like this one because it has some ends to keep the poo in when you remove it
Here animal enclosures have a different set of rules for permitts... But you can build a 12 x 12 shed without a permit providing its not plumbed or wired. There are ways around that of course. Non fixed on a foundation Is a great solution as well. Cattle panel coop has excellent snow load bearing capabilities Lots of tractors are made from cattle panel construction. Take a look at the coop page... Just be aware you may have to anchor it with wind anchors during storms or windy days.
answered above for both chickens and guineas.
I use dog kennel panels... Just remember it has to be predator proof Night time.... and Be dilligent on your routine for getting them to come in at night. Predator losses occure at night if they are allowed to roost in the trees. that goes for chickens as well.
Raising to gether is good... Chicken raised guineas tend to be calmer. One thing to remember As the Guineas mature and become Sexually mature they will start pairing up... The males will chase each other wings raise behind them showing off for the girls while the girls ignore them.... nice thing about having a flock is if there are more males than females the males will form a bachelor flock. All will care for each other during a threat.
During this first year is when they may get aggressive to the chickens... And when they attack they all attack they dont keep it one on one like Chickens do. The next year everyone is more relaxed with only a few scuffles
Probably I know they use something similar at the San Diego zoo...
Dont know.... have never used Deep litter. YOu might ask some questions on one of the deep litter threads.
I suspect the jumbos will be only marginally slower. If you look at em with out their feathers they are a very long legged bird.... explains why they can run so fast even though they look stumpy Football helmets in profile.....
Dont think it will make a difference
Glad to put in some input.
deb
I loved all your humorous posts about them (and you almost talked me out of them a couple times lol). One thing I thank you for reminding me of is not to let your animals start thinking of you as one of them.... particularly with these girls, who aren’t getting any littler... 
