Layer feed and layer pellets are the same thing except for the texture, or the sixxe of the pieces. "Granules" and "pellets" refer only to the size of the pieces. Baby chick feed is in very small granules, grower and flock raiser granules in larger pieces. Pellets just means the feed has been formed into pieces that don't fall apart, so you get a lot less "dust" at the bottom of the feed bowl, and therefore less waste. But the pieces are big enough that the chicken needs to be near full size, as they are when they start laying, to handle them comfortably. Some people find their chickens seem to refuse the pellets when they are accustomed to a crumble texture, but actually, if they have only pellets available, they will accept it fine when they get a bit hungry.
By the way, you should not mix scratch with their regular feed because they will pick out the scratch and leave the rest. Think of scratch as candy -- it's fine for a treat but you have to be sure the kids eat ther regular meals, too.
Layer has extra calcium to help the hens make strong eggshells. Grower is intended for chicks about 8 wees to laying age, but is also fine for mature flocks, male or female. While many people do feed their roosters layer, it is best to feed a flock raiser feed so that the males don't get that extra calcium, which can cause harm, expecially long term. Since you have cockerels, if your feed store doesn't have flock raiser, ask them to order some -- or just use grower feed as your adult feed. You will also want to offer a small bowl of oyster shell so it is available for any laying hens who need it. You will be surprised how little of this they eat, even when fed flock raiser without the added calcium.
Here is an article about some effects of excess calcium :
http://www.hyline.com/aspx/redbook/redbook.aspx?s=5&p=36
