The varieties of Coturnix don't really behave differently from one another, because they are separated by (sometimes single-allele) color mutations and size/egg-laying proficiency. They aren't separate breeds, like you get with chickens.
You can keep two females just fine as long as there aren't any males around (but three bachelorettes would be better, so one doesn't get lonely if their only flock-mate dies).
My birds live on the ground in an open-air aviary and have seen my cats since the day they were hatched. Only one of them even acknowledges they're there (and she's nervous to begin with). As long as they have early exposure and feel like they always have the option of getting away from a predator, they shouldn't get too stressed.
Coturnix are only people-friendly if you hand-raise them and continue contact with them into adulthood. Mine come running to me when they see I have treats, but are otherwise indifferent (no desire to be held, etc.). They let me pick them up and examine them, but only for short periods of time. I've never been attacked by my quail.
These quail can be kept together without being debeaked, so long as your flocks are single-sex or your male-to-female ratios are ideal. You shouldn't get fighting so long as the gender issues are managed around spring and summer, and as long as you give the birds plenty of space (more than 1 sqr foot per bird) and things to keep them occupied (treats, dust baths, things to climb, etc.). Widespread fighting in a flock is typically the fault of the owner; always look for ways you can improve birds' living conditions before you choose to mutilate them.
I've never tried giving mine whole corn or oats, but I imagine those foods would be too large for them to grind down completely (remember how big these things are in relation to chickens). People usually feed their adult quail 24-30% gamebird feed, or get a high-protein blend mixed locally. Do not try to replace this with typical chicken feed, as it won't have a high enough protein for these fast-growing, fast-aging birds.