I'd keep four or a couple dozen, lol. You'll enjoy them. Males and females show gender by two weeks. My last hatch I was in denial until about 4wks because I had only 1 pullet out of 7. I kept thinking the more messy colored ones must be girls. Nope. At two weeks if you see black anywhere, then figure they're boys, especially on the chest or legs. Females have cream chests and leg feathers.
I'm raising a m/f pair of Faverolles right now, they're just at 6 weeks! I thought the same thing as you about the black, when their wingtips came in black at 1 week I thought they were both cockerels. But lo and behold, the 2nd row of feathers came in tan/brown and sure enough, she's a pullet! I was making guesses at 1 week, but I was completely certain at 2 weeks old.
as for temprament, they were really really flighty and timid as chicks but I have won them over with handfuls of ground oatmeal. they're very friendly now I am raising them with 14 wyandottes who are 3 weeks younger. I hope that this will help to address pecking order issues by having the Favs at the top as the oldest. The little wyandottes seem to think the Favs are their parents, I swear they will even try to sleep under the pullet's breast. They copy everything she does as if she were a hen. I hope this makes for a fantastic broody mama when she's older!
here are some pictures when they were little and I was trying to sex!
1 week old - see the black on the wings and the back? that is the PULLET! omg
2 weeks old - pullet
2 weeks - cockerel