Welcome to the forum. Glad you joined.
People have been raising dual purpose flocks that way for thousands of years. It is a very cost effective way of getting eggs to eat and you can also eat old hens or extra roosters. The meat is not as tender nor abundant as the Cornish X that we have been raising since the 1950's but people have been eating chickens like that for a long long time.
You have three basic types of meat birds. The dual purpose that I mentioned above. Those are pretty slow growing compared to the others and need to be harvested later, which means the meat can be tough if you aren't careful how you cook it. Some people butcher them at 16 weeks but I prefer at 22 weeks. I'm more limited in how I can cook mine but I prefer the flavor. There can be a lot of personal preference in whatever you choose to go with. Compared to the others there is not a lot of meat on the carcasses but I can easily get two meals for two out of a small pullet. A larger bird just means more chicken for my lunches.
The Cornish X are the commercial meat birds. They are very efficient at packing on meat, they grow very fast. Some people do pasture them but they also supplement their feed a lot. These are typically ready to harvest at 6 to 8 weeks, that's what you see in the store. Butchered at that age they are very tender no matter how you cook them.
Then you have the Ranger types. They grow faster than the Dual Purpose but not as fast as the Cornish X. They were basically developed to be pasture raised but people still tend to supplement their feed a lot. As Molpet said they will grow slower on pure pasture. These are typically ready to butcher at 12 weeks. You can cook them practically any way you wish. They will have a bit more flavor than the Cornish X.