In general, the productivity of the offspring will usually be somewhere in between the productivity of the two parents. Since roosters don’t lay eggs you don’t know for sure what they are bringing to the mix. But if you know what the rooster’s mother or grandmothers were doing or have the rooster’s full sisters you can get a pretty good idea. I’ll use weasel words like “usually” or “in general” because no one can give a guarantee on an individual, but we can give you trends. If you hatch a few pullets from any of those mixes you will get most of them somewhere in between the parents as far as egg laying. By most I mean a lot of them in between, the ones not in between will be pretty rare.
I don’t know exactly what your goals are. The number of eggs maybe more important than the size of the eggs for all I know. You may have other goals.
I don’t know if your Ameraucana are true Ameraucana or really EE’s. If you got them from a hatchery they are almost certainly EE’s. It doesn’t matter. You have enough to see how that part of your flock are laying. If you cross your Ameraucana roosters with those leghorns you should get pullets that lay as well or better than your Ameraucana hens and the eggs will probably be a bit larger. The pullets will probably be somewhere in size between the two breeds.
Especially if you got him from a hatchery that Barred Rock should come from a flock that lays well. You’d probably be happy with those pullets too.
That Silkie rooster is more problematic. Silkies are generally bantams, lay small eggs, and usually don’t lay a lot of eggs compared to your other breeds. If egg productivity is your only goal you probably will not be that happy with his pullets. Silkies tend to go broody a lot, those other breeds don’t. If you use that Silkie rooster you could get some pullets that tend to go broody.
I don’t know why someone told you to not use ISA Browns for breeding. ISA Browns are hybrids and are commercial production hens so they can be a little more delicate than the other breeds you have. Since they are hybrids feather color and some other stuff won’t breed true. But by mixing them with your roosters you make the offspring a lot less delicate and they should pass on the good egg laying traits to their offspring.
Without knowing why someone told you to not use those ISA Browns it’s hard to argue. A lot of this is opinion too. But in my opinion you’d probably be really happy with the chicks from your Ameraucana or Barre Rock roosters over them, same as the leghorns. I’d have the same reservations with the Silkie rooster as above.
