I have 2 female together with no problem and they are in a cage no bigger then a 10 gallon fish tank,
as a matter of fact I did have my first button quail in a 10 gallon tank.
Let's put it this way, when the babies hatch, they are about as big as a bumble bee, their eggs are about as big as my middle fingernail, and the adults can easily git through an opening 1" square, without any trouble. So they are pretty tiny. Budgies (parakeets) are bigger than buttons are
You can keep pairs of any sex-combination together, just so long as there aren't a whole bunch of males in a group. My groups have too many males, and some of my poor girls are looking a bit haggard.
ETA: I guess my right hand was feeling a bit left out, that is supposed to be 'get', not 'git'...I'm not that much of a hick!