First decide what you mean by “meat bird”. What traits are you after? Does color matter? With a white or buff bird you get a prettier carcass if you pluck. With a darker bird you can see the pin feathers. If you skin it doesn’t matter.
Will you be eating the females? Half the chicks I hatch are female so half the chickens I eat are female. So are you looking at traits for both sexes or just males?
How important is size? Many people are obsessed by size but there are only two of us. We can make two meals off of a fairly small hen so we don’t need extra huge chickens. That’s why female work for me.
How will you cook them? You can get varying opinions about at what age you can grill or cook but practically everyone agrees that the older they get the more challenging that becomes. If you are happy with cooking them slowly and with moisture you can get some really nice older birds. If you want to cook them hot and dry, you better process them early.
How do you feed them? If you want a young bird to eat and are buying everything they eat, you need a bird that is at your butcher weight pretty quickly. You want one that gains meat fast though he may not be all that big. If you are happy with an older bird that forages for a lot of what they eat, how quickly and efficiently they convert feed to meat may not be all that important. They could eventually get big without you spending a fortune on feed.
How much freezer space do you have? This is more pointed toward the Cornish X than what you are talking about, but consider if you have sufficient space when you prefer to butcher. Just part of your planning.
How important is white meat versus dark meat to you? Different chickens have different conformations so you can get different proportions of dark versus white.
That’s enough. Hopefully you get the idea of what it means to decide on what traits you want. Once you know what you want, select as your breeders the ones that most meet your requirements. If you consistently do that you should get closer to what you want each generation.