When they're sold by single color varieties then you can be sure they are true Ameraucanas, and not Easter eggers. Cackle has quite a few color varieties. I was surprised to see buff Ameraucana since those aren't very common.
That is an unusual cross, so I doubt anyone else has the same thing. I'm surprised their legs don't have more feathers, but you just never know with mixes, sometimes.
It doesn't fit for any pure breed McMurray sells, so likely a hybrid. 'Ameraucana' maybe. McMurray's Ameraucanas are Easter eggers and can look like anything, just about.
They are different in coloring, but that is not going to tell you gender at this stage. It's just natural variability of hatchery chicks.
Around 6 weeks is a good time to start determining gender. The good news is they both have small combs and wattles, so are probably females. But not for sure...
Wattle growth is inhibited in bearded chickens, so it is not a good thing to judge by in bearded Silkies. You have to go by combs at this age, and even then it is guess work unless you have a really obvious boy.
My guess is 1 is female and 2 is male, but that is only a guess. If you really need...
Barring is always white over a different background color, usually black as in barred rocks. Neither of these birds is barred. I think they are both pullets.
The chicks also would have had white spots on the back of their heads if they were barred.
I think Easter egger x laced Wyandotte pullet, but I wouldn't be surprised if I was wrong on gender. I'm putting weight on its small and pale comb, plus the slender legs, rather than color pattern in this case. The hackle is pretty well developed as well, but my gut is saying female for this...
At 6 months males will be really obvious, and I only see the one you already know about.
The black one has no male specific feathering and the wattles are a normal size for a non-bearded female Polish of that age.
The rest look to have beards, and that conceals and often eliminates wattle...
They are a hybrid, and often look a lot like brown Leghorns, but their looks vary a lot from bird to bird. Searching Google Images will turn up some pictures. They are bred to lay lots of green eggs.