An Ameraucana is bred to some very specific standards (most all of them come in solid colors), an EE is bred from an Ameraucana and something else. (ie barred rock, rode island red etc. they are multiple colors consequently) They are considered "mutts" in the chicken world but come from some great lines sometimes depending on the parents that are used. I hope that helps.
Yes, egg size and color can vary quite a bit. Even chicks from the same line can vary in their size and shape and color.
