I think I fed the starter feed (non-medicated) until about 16 weeks and then changed them over to  an All Flock feed. For a short time after the girls began laying I gave them layer feed, but have switched back to All Flock. My preferred brand is Country Lane All Flock Crumbles, but when they are out I get Nutrena Nature Wise All Flock Pellets. They seem to prefer the crumbles over pellets.
Layer feed is not necessary, but more of a choice. It does have added calcium that the boys don't need.
Edited to add: Wasted feed stinks..... I've tried a lot of things, and what is working best for me now is that I un-hung the hanging feeders and instead placed one in one of those big black rubber bowls. Now the feed falls in the bowl, but there isn't enough room to scratch it all out.