That helps quite a bit. I was obviously off-track in my other post.
A lot of the confusion is because so many different things can work and we keep them in such different conditions. There are very few things where there is just one simple answer that is correct for each of us. Not all hatcheries offer the same chickens either. You have different people at each hatchery selecting the breeders and they will choose for different traits. I've gotten Speckled Sussex and Black Australorp from different hatcheries. The basic colors and such were fairly close, but there is a clear differene in configuration and some other things.
Take the red broilers. There are different red broilers from different hatcheries. They don't all have the same genetics. They will grow at different rates. Another big factor is how you feed them. If you feed them a high protein feed with it always available and keep them contained so they don't exercise and walk it off, they will put on weight pretty fast. If you feed a feed less high in protein and let them forage for some of their feed and get exercise while foraging, they will put on weight slower. I don't know which specific hatcheries you are talking about and I'm not that familair with red broilers anyway, but I can easily see where you can get different projected butcher ages from different hatcheries.
As far as bedding in the brooder, we use a lot of different things. paper towels, wood shavings, and sand are some of the more popular, but there are plenty of others. I don't use bedding in the brooder any but raise them on wire instead. One potential problem with newspaper is that it can be slick. They can slip and get splayed legs. If it is shredded, it is no longer slick so shredded newspaper would work.
I'll also point out that there is a difference in what can happen and what will happen. Not all chicks raised on newspaper get splayed legs. If you raise them on newspaper, maybe none of that batch will. But it can happen so it is best to avoid newspaper.
I can understand your frustration, but raising chickens is not cookbook where you have to do exactly this or you will have disaster. There are many different things that work. You do need at look at what people say and see if they are talking about conditions similar to yours. A lot of people post like their way is the only correct way and that is almost always just not correct. We do things in many different ways. You need to pick which of those many different ways will work in your situation. The good thing is that if you provide the basics of food, water, and shelter they will probably do OK.