I look for many things when studying my chicks to know what to keep and what to let go and what to remove from any breeding program. Study the SOP for bantam Cochins and work from that.
I like to look from above and see how wide they are, even from an early age. That isn't too difficult because that is the view I see most when cleaning the brooders every day.
I want to see a fairly square chick but that may not help you understand what I am seeing.
If you already know what is boys and what is girls then yours are certainly at an age where you can pick the better birds.
My roos need a short back with a good wide chest. Their combs should not have a lot of extra points on them and should not be too big for their head. The eye needs to be bold and large on the head. I want to see the wings held well up against the body but most of the time that is a challenge in my breeding program. The legs should be short and well formed, not turning in or out because then you could have pelvis issues and that is a problem in the entire bantam Cochin breed.
Your pullets can have a slightly longer back but not so long as to have them look like you could roll a skateboard from the top of their head down the back and up the tail on the other side while looking at them in profile. Or you can call it a ski slope look. However, you get too short of a back and you won't get many eggs to breed on that beauty and the roo has a harder time staying on her while breeding. Major down fall in breeding bantam Cochins. So many folks have to AI and blame it on the fluff. Just breed a better bird, imo. Fluff has not bothered mine too much.
When you look at yours in profile try to picture them as the shape of a basket ball. So many can look like a heart shape and that can be worked with. It is better than some alternatives I have seen.
Not sure this helps much. If you are like me, you are more visual. All I can say is look through this thread and the Cochin thread and see all the different things people breed. We all have a different way of looking at the SOP and interpreting what it says. That is the reason a different bird wins under different judges even on the same day at the same show.