as chicks in fuzz no you cant sex them, but as soon as they start to feather out, the HEN's tail feather will explode in length and the male will stay short, it's actually backwards from what you would think. Once about half grown the males will catch up and surpass them pretty quick, but the initial feathering is more dramatic in pullets, mainly due to the fact that most all chicken pullets feather quicker than males, this is the same reason you can feather sex some day old chicks by the wing feathers in some breeds. The pullets will already be opening up as soon as they dry where males will be solid pin feathers, same concept in phoenix tail growth.
As for info about them, well they are one of my favorite breeds of course, I have them in bantam size in 11 different colors and counting.
I agree, they are very gentle birds, actually I keep multiple males in all my breeding pens and they get along just fine, never been spured by one, and do have many tame hens that will ride on my shoulder.
They are very calm, never seen a flighty one. With mine, they arent broody at all, but then I never give them the chance either, take the eggs daily.
If tail lenght is a concern to you, the males need to be kept high and dry. Fully covered pens and high roost with heavy straw beds on the ground of the pen. If you have pens that get wet when it rains, all you'll get is ground length feathers as the mud will break them off.
Also keep as few birds as possible with him, for best tails, actually keep NO birds in there with him. Others will step on his dragging tail and pull out , fray, or just break off sections of it. Those are the 2 main things to do different , keep them dry and clean, and very few pen mates.
Aside from all that, to me there is no better breed out there, well maybe d'anvers, hey I got nearly 30 colors of them, so I'm kinda partial to them too.
But phoenix are a great bird, very beautiful, and a joy to keep and watch