The reason you are confused is that there is no one right answer that fits everybody. A lot of different things work and people have a tendency to think what they do is the only right way. That comes across in their writing and advice. Some chickens start laying as young as 16 weeks. Some wait a whole lot later than 22 weeks. When they start to lay, they need extra calcium for the egg shells. Go by when they start to lay, not by a calendar. With that age difference offer oyster shell on the side for the calcium instead of switching to Layer.
I don’t know what feeds are available for you so I can’t make any real suggestions based on what is available to you. Personally I’d be happy feeding all of them at those ages anything between 15% and 20% protein content and offering oyster shell on the side for the calcium when they need it, but mine forage a fair amount so percent protein in the feed I give them is not all that important. If all your seat is the prepared chicken feed you give them, it becomes a little more important. If you give them specific treats that are low in protein, they may need a higher protein feed. If you give them treats that are high in protein, a lower protein feed may be in order.
In spite or a lot of what you read on here or hear from others at the feed store, we all have different conditions so different answers apply.
