It's funny, our Light Brahma male was the most obvious cockerel ever, from day 1. He was bossy and did everything first except grow his tail and wingfeathers. His feathers came in a lot later than the others.
By 3 weeks (2nd picture), he was much bigger than the others, his legs were thicker, and his comb had little ridges the pullets didn't have. By 4 weeks (3rd photo), his comb was turning pink, and he had pointy hackles on his neck.
He was our first cockerel, so I thought they were all obvious like that

But for some cockerels, you don't know until they lay or don't. Also, some hens take on rooster traits, like crowing. Our little head hen tidbits for her flockmates.
View attachment 2455036
View attachment 2455042
View attachment 2455043
View attachment 2455052