After processing they need soaked in a iced salt brine for 6-24 hours and then rested in the refrigerator for 4 days before cooking or freezing. Otherwise they'll be tough or chewy or stringy. We process around 20 weeks for a higher meat yield, from breeds that are truly dual purpose and bred for it. Instead of "used to be" dual purpose that have a more efficient layer body type instead.
Body shape varies dramatically between individuals within the same breed, depending on how they were bred. Typically the hatchery birds have a leaner and more narrow build to them, while breeder stock is wider and fills out a baking pan better.
The different breeds vary widely too, from how much meat is on the breast versus how much is on the thigh, if the thigh is dark meat or white meat, how thick the skin is, the color of the skin, where fat deposits happen and if they're prone to globby fat.
The way they're grown out/finished has a subtle effect on flavor/texture as well. I start them all on Turkey starter, dropping the protein every 3-4 weeks from 26% to 24% to 22% to 18% by the time they're 18 weeks old. Then I introduce sweet feed and a lot more greens for the finishing, anywhere from 4 to 12 weeks of that.
The first extra cockerel we invited to dinner though... after hours and hours in the crockpot... almost never ate chicken again. Hahahaha The dogs didn't mind the texture.
Now though, I'm hopeful for boy heavy hatches for the freezer! It took over 2 years to figure out what our methods were going to be once we went dual purpose.