Bob,
Those are some nice plants!
Your variegated plant really reminds me more of A. mapisaga than A. americana. The mapisagas they have at the Desert Botanical Garden in Phoenix are just as floppy with curly leaves, none of the truly large americanas I have seen are that floppy, but people have been calling these A. americana variegata for a long time now so we will probably not easily figure out the true heritage of that plant.
The pictures of your americanas are definitely distinct. The second plant looks a lot like the landscape americanas you can see all over the place here in the landscaping, to me that is a classic A. americana. The first one could be what people are calling A. americana var. expansa which is definitely pretty blue and has smaller teeth. That plant also looks like something that I have which is probably Agave lurida, but came to me as Agave 'sawtooth' a name a friend gave it because he did not know for sure what it was. Not quite a classic americana and also not franzosinii. So he coined it saw tooth, not being familiar with Agave lurida.
I have a few pups of that plant and they look a lot like your first americana, and are very similar to the Agave lurida at the DBG, so that is also a possibility, but there are a good number of americana varieties out there, so that is probably it.
