First Ever Backyard Chickens!

We are at the week 4 mark with my first ever backyard chickens.... got some easter eggers straight run from a local supplier and I'm wondering what to keep an eye out for to determine if this blondie is a Roo. I'm pretty sure the black one is a hen (pullet) because she has rounder wings, hardly any developed comb, and skinny legs. Her demeanor is more confident and feisty though than the blonde one. The blonde one has earlier feather development, a larger comb and red on its wings which I've heard all usually indicates males... but it also is shyer and less curious than the black one and has skinny legs like the black one.

If I do have a Roo I have someone I can swap with since I'm not allowed to keep a rooster where I'm located. If blondie is definitely a Roo I want to swap him out early so that I can form as much of a bond as possible and integrate a new hen in with the black one, as well as giving blondie as much of a chance as possible to integrate into his new flock.

I know it's still a little early to start noticing sex traits but I need to decide if I'm swapping or not by the 28th so that we can make the trade before having a rooster becomes a problem. What kinds of things should I look for to determine whether I should go ahead and swap the blonde one out?