This topic is better suited to the guinea fowl forum, but here's what I know.
After keeping chickens off and on for 25+ years, I ended up getting a mixed flock of chickens and guinea fowl in August 2022 (15 of each). I live on about 16 acres of land, of which I have about 5 acres fenced off for the free-range flock, about 2/3 of which is wooded.
First off, a lot of the information you find online about guineas is either wrong or poorly presented.
They will need a separate sleeping area, but it doesn't necessarily need to be a completely separate structure. My mixed-flock setup has two coops with a fully enclosed run in between with roosting bars. The guineas tend to occupy one coop, the chickens the other, and the run is sort of neutral territory.
I haven't noticed that guineas are particularly more voracious at eating bugs than chickens, but they do tend to cover more ground in a day. I don't think they'll do anything for mosquitoes, though. They do wreak havoc on ants, beetles, and joro spiders, though.
I don't know where you got the thing on them being dirtier. They don't seem any more filthy than chickens.
Guineas are very flock-oriented birds. If one or two get separated from their flock they tend to freak out. The general consensus is you need at least 10 to get proper flock dynamics. I have 15 (plus 16 to 21 chickens).
Most times guineas aren't, in my opinion, that noisy. They are extremely territorial so if your property borders a public road or you have other traffic they'll scream at passers-by more often than if your property is more isolated.
Guineas are pretty pushy but I haven't noticed any particular problems with my chickens. The worst time is early spring when the male guineas get more aggressive as part of their mating rituals. That will tend the stress out the chickens as the guineas tend to charge at everything.
Guineas do have some different dietary needs when they're young, and they're more delicate the first couple weeks after hatching. In particular they're more vulnerable to chills. Keep keets away from drafts and make sure any water you give them is at least room temperature. They need game-bird or turkey starter the first 8 weeks, then you can put them on chick starter the next 8 weeks. If you're raising chicks with them at the same time you can feed the chicks the same diet with no problems as far as I've seen.
As far as breeds go I've only had experience with French Pearls. They're on the larger side which I think is a positive because they're not as flighty and they seem to freak out predators more when they charge them.
