Hello and welcome! I'd imagine if your only allowed 2, that your most likely not allowed a rooster. 2 hens would be great! If I were only allowed 2, I'd pick a good layer like a rhode island red, sex-link ect... Leghorns are great layers, but very flighty and hard to handle. Easter eggers lay pretty well and lay blue or green eggs. It's best to research breeds or ask here.
Third: Def. go with two females.
4th: Chicks or older pullets??? There are pros and cons. If you want females, then you need to find sexed chicks, and that's not always easy to do. So older pullets are easier to find with certainty of sex. Of course chicks are nice, because they tend to grow up tamer as long as you've handled them a lot. But that means more time and expense in that chicks need to be brooded for several weeks. Flip back to older pullets and you get eggs a lot sooner, and don't have to fool with brooding. So weight the pros/cons of each and choose which works better for you
I would get two hens. And personally, I would pick a hen that is an excellent layer like a Golden Buff, also known as Red Sex Link, or Cinnamon Queen.....there are several different names for that type of hen. Mine lay a big brown egg nearly every day, plus, they only weigh around 4 1/2 lbs, so they eat less feed.
Another good layer that I really like is the Barred Rock. I have one, and she's just beautiful and lays a nice big brown egg.
Black Australorps hold the record for most eggs laid in a year, and mine lay well and are easy to handle. Or get two different breeds, so you can easily tell them apart. I agree, definitely two hens -- I love my roos, but one roo with one hen will mean the hen will get overmated. As for chicks or older chickens, just get both the same, whatever you get. Mixing ages has its own set of difficulties, and may well mean keeping them separate for a few months, and would also mean chickens living by themselves, which is also not good as they are flock animals.
The catch on older birds is, people are prone to selling off their older birds who have slowed down or even stopped laying, saying they are younger than they are, so it depends how well you know the source. Once a chicken is full size, it's virtually impossible to determine age.
I say go for 2 hens. My favorite breed are Buff Orpingtons. I honestly don't have experience with any other breed. We have 3 (started with 4 but one was killed by a predator). They are the sweetest, friendliest birds. They love to cuddle and be held. They follow us around and come when we call them. They are great layers (so I've heard, mine have not started yet as they are still too young), even in the winter! I give a huge vote for Buff Orpingtons. Ours were hand raised. Check out my BYC page and you'll get a good idea of their personality. But don't take my word for it. Research the breed and you'll fall in love before you even decide! ❤ https://www.backyardchickens.com/web/viewblog.php?id=86573