As has been mentioned, it's the hatcheries that do the sexing, by checking newly hatched chicks vents, before they are sent to the stores. Be aware, vent sexing is kind of an art, and even the best vent sexers have an 80 to 90 % accuracy, so even buying "sexed pullets" can result in an accidental male. Be aware, also, that TSC is notorious for mixing up their bins of chicks, and based on many posts I've read on here, sometimes those mix ups happen at the hatcheries too. So if you can't have a rooster, be prepared with a plan for any cockerels that may pop up. I'll be blunt here, most often they end up in freezer camp, think about if that is an option for you, you will get attached. Finding pet homes for the boys is very, very hard, because the "market" gets flooded rapidly, and again to be blunt, Easter Eggers, as a mutt, are not in high demand as breeding roos. If you need to be sure that you don't get a boy, consider started pullets, or forget the colored eggs, and get sex links, or look for a rescue to get hens from.
To answer your second question, I've have several EEs, and generally, they are nice hens. Mine have laid light blue or green eggs, pretty but not intense color. Personalities vary, as with any breed. I do not have personal experience with cream leg bars.
