Hi there.
Going with either a
"grower" or flock raiser (the FR, with 20% protein is my preference, but for the juvie's aim for 18%+) with your OS on the side like you intend is a fantastic way to make sure all your birds get what they NEED (not like)... all the treats mentioned above are EXACTLY that treats that are in many instances high in fat content. They should NOT be offered at a rate of more that 10% of total daily intake and should NOT be mixed in with the standard feed but used as a TREAT... that gets associated with you.

Excess treats can also lead to fatty liver hemorrhagic syndrome/sudden death... often contributed to heart attack when folks don't get necropsies to find actual cause of death. Again, those birds are often genetically predisposed... seen commonly in Orpington as one example.
For what it's worth... Since learning the difference many years ago... I never use "layer". All the terms used by different companies can make it pretty confusing. The main difference between most feeds will be protein and calcium content. Their will be minor differences in other vitamins and nutrients.
Since feathers are made from 90% protein and its' amino acids... some folks switch to higher protein feed during molt. Please note "feather fixer" is still loaded with calcium (equal to layer at about 4%)... which, EXCESS amounts (>3%) fed LONG TERM to birds not in lay (juveniles, roosters, broody's, molter's) *can* (doesn't mean will) cause kidney issues including gout and even failure or sudden death... most often in birds genetically predisposed somehow AND also fed excess treats or accidental dehydration.
One other thing since I see you're in Michigan and I too often see the MYTH that feeding corn will keep your birds warm... that is total hogwash spread by folks who don't understand basic metabolic behavior... in that a calorie is a calorie is a calorie and birds are wearing down jackets that keep them warm in addition to their bodies burning calories for energy no matter where they come from. So DON'T dumb down you nutrition by offering low nutrient snacks like whole or cracked corn... while they DO provide energy they are only about 8% protein and while our feed are often made from mostly corn... it has the vitamins, minerals, and importantly amino acids added in.
Proper nutrition... is the key base after genetics to all things health related, IMO. Keep a great foundation... battle less internal and external parasites... and less issues if/when viral or bacterial concerns don arise. A healthy and strong immune system makes a ton of difference and can be heavily influenced by our provisions.
Hope this is helpful!