Yes, males do tend to feather in slower than females. Also, roosters will develop bigger combs and wattles earlier than hens. Around week 16 they grow will saddle feathers. Males will have pointy saddle feathers and females will have rounder ones. As far as age, it really depends on the breed. Some you won't be able to tell gender until around week 18 and sometimes birds are sexed on hatch date.
I'm asking about a Black Australorp, I tried the wing sexing when they were a day old and of 2 BA and 2 RIR the one BA's wing feathers were shorter than the others and now at a little over a week that one's feathers are still shorter than the rest. So i'm thinking it may be a rooster.It was born third but is smaller than the others.