It's not a good idea to feed layer feed to any chicken that isn't currently laying eggs. This includes chicks under 18-20 weeks old, molting hens, old hens and roosters.
The damage caused by excessive calcium by a bird that doesn't need it (in the layer feed) can be very bad (kidney damage and visceral gout) in chicks and will also affect older non-laying birds, but over a longer period of time.
If you haven't bought layer feed yet, don't. If you have and haven't opened the bag, I would return it and exchange it for a bag of grower.
Feed grower until everyone is laying and keep a dish 24/7 of crushed oyster shell on the side, for calcium. Your birds will instinctively know if they need more calcium or not. Once everyone is laying eggs, you can either keep feeding this way indefinitely or you can switch to layer feed.
The only problem with layer feed is when your hens molt. Molts will last 2-3 months. If they all molt, then you can just take them off layer and feed grower (with oyster shell on the side), because they won't be laying eggs and shouldn't be force fed extra calcium. When the calcium is mixed into layer feed, they can't pick and choose how much calcium they get. When it is offered on the side as crushed oyster shells, they can pick and choose. But if only some of your hens molt, the grower/oyster feeding plan will also work, because everyone can eat the food safely and those needing calcium for eggs (because they aren't molting and are still laying) can get what they need. If they're molting, they will mostly leave the oyster shells alone, but may peck at it occasionally. But feeding layer feed to a complete or partially molting flock is not a good idea, because of the excessive calcium thing.
The only real difference between layer and grower is the extra calcium in layer feed. Grower also is usually a bit higher in protein, which is good for molts anyways and good if you like to feed them low-protein table scraps and/or scratch grains.
Layer feed is a hassle, because if your flock does molt and you switch to grower for a while, then you will have an open bag of layer feed left over. By the time they are done molting, your open bag of layer will not be fresh enough to use any more. When choosing feed, decide if organic/non-gmo matters to you first, then look at the freshness date (stamped on the feed tag of the bag), then look at the ingredients. Stale/rotten ingredients are not better if they are better ingredients than fresher lower-quality ingredients.
Instead of grower feed, you can also feed "all flock", "flock raiser", chick starter, broiler, game bird feed, turkey grower or turkey finisher. Any of these will work, with a side dish of crushed oyster shell, always available.
Lots of people feed layer feed to all their birds, from chicks, molters and roosters and say, "I've never seen any problems with this and this is what I was told to do." The problems created by excessive calcium are internal. Chickens can't expell unused calcium (calcium that would be expelled in the formation of eggshells), so it will get built up in their kidneys and other internal organs, causing calcification (hardening) of these organs. Eventually, these internal organs will fail. Chicks can develop leg deformities and have trouble walking for their entire lives. Older birds will just fall over and die one day and people will chalk this up to "chickens die". Chickens do die, like everything else, but they always die due to some cause. Without a necropsy (post death inspection/dissection), death by excessive calcium can be impossible to "see".
