I think the pecking order works pretty similar to a pack of wolves, at least MY flock dynamics are similar.
I have 5 pullets. The "Alpha" hen is my 18 week old Barred Rock named Joon. Whenever somebody gets too close to her, or does something she does not approve of, she races over to put them back in line. She is best friends with my LOWEST ranking pullet who is an Easter Egger (same age) named Munk. Munk get's bullied by my other three girls whenever she is away from Joon. But if she is with Joon, nobody messes with her. And Joon NEVER hurts her, ever.
Second in command is my 24-28 week old Brahma named Monica. She tries so hard to buddy up with Joon, but Joon won't have it. Monica takes it upon herself to keep the two youngest pullets in line. Which brings me to Phoebe and Butternut my two 14 week old Wyandottes. They are somewhere between Monica and Munk, but they are always fighting it out between themselves who is first lol.
The flock hierarchy goes on for life I think. I know Monica is waiting to take Joon's alpha position, and occasionally will make this clear with a pretense chest bump or motion toward Joon. No luck YET, but it's like a Beta Wolf just waiting for the Alpha to fall so he/she can take over.
P.S. Chicken size does NOT matter LOL. Joon was 16 weeks old and had this HUGE 24 week old Brahma in CHECK. The Brahma is about 2 times Joon's size, but she runs quite willingly. It's funny to see this little Barred Rock tailing this big old Brahma Mama haha.