I think it is a cockerel, too. The pictures aren't too clear, but the size and color of the comb indicate a male at 12 weeks old. Females would generally have smaller and paler combs at that age.
Tough to say for sure. Both are bearded, and they probably got that trait from the OE father. OEs aren't typically white, so the mother of the white chick probably was. Maybe a Leghorn or white rock. The other isn't as easy to tell, but when it's older it might be easier to make an educated guess.
It's either a cockerel of another breed or a Sapphire Gem pullet that is developing early. Male SGs should have the white spot on the topside of the head and barring, but this has neither.
1 buff Orpington female
2 buff Orpington male
3 blue laced red Wyandotte male
4 maybe a splash Andalusian or some type of hybrid. Female.
5 black lace3d red Wyandotte male.
The gray one is an Easter egger, as you guessed.
The blue one could many breeds-- blue Australorp, blue Andalusian, blue Orpington, etc. It is a dark shade of blue, not black.
She could be a Sussex mix, but one of her parents has a pea comb, which is dominant over regular single combs genetically. To me she looks like some kind of Easter egger. So maybe she'll lay blue or green eggs.
1 Rhode Island red
2 Blue Andalusian, blue Australorp, blue Orpington, blue copper Marans
3 Partridge Plymouth rock
4 Welsumer
5 barred rock
6, 7 maybe Easter eggers
8 same as #2
9 cuckoo Marans or maybe olive egger
I edited, but it still might be off
12 weeks is when the males usually start showing male specific feathers. Those are the long, slim, pointed feathers males get in the hackle and especially the saddle area.
But in the meantime just keep an eye on the comb and wattles for increased size and redness. If things stay pretty much the...
As far as space goes, I think you'll be okay for another couple of weeks. But then you should move them to a bigger space.
As far as the heating plate goes, I would probably leave it the way it is for a while longer, until some of the smaller chicks get more feathering.
The comb/wattles are pretty well developed for that age, but not to the point where I'd say it's for sure a male. I think this one will simply take more time than most to tell.