What would you say is the meat quality from that age? Is it like soup only tough or still ok for general use?
At that age I would not try to fry or grill them. I'd skip roasting also. You can bake them, pressure cook them, slow cook in a crock pot, or use in soups or stews. Regardless of how you cook them you need to age them past rigor mortis or cook them before rigor mortis sets up.
Meat quality depends on the preferences of the person eating it. The meat you buy will be pretty bland tasting (to me) as they are usually around 6 to 8 weeks old when they are butchered. If you are used to purchased chicken meat you may not like it. Some if us prefer the taste of "older" chickens.
Other than pressure cooking (which works great) you should cook the meat slow and moist. Coq au Vin makes a gourmet meal out of an old rooster, let alone an old hen. Chicken 'N Dumplings is pure comfort food and a good way to stretch a small hen for a large meal. Old hens are great for chicken soup. Do not bring it to a hard boil, just simmer for a long time.
My preferred way to cook an old hen is to part them and put serving parts in a baking dish that seals well. Add carrots, celery, onion, garlic, and herbs in whatever combination you want. Cook that at 250 Fahrenheit for about 3 hours. Carefully remove the meat with a slotted spoon. Carefully because it may fall off of the bone. Strain any liquids in there and you have some of the best broth you'll ever have.
When I butcher, I save the back, neck heart, gizzard, and lower legs and feet. I skin the legs and feet to get them clean, most people skip using the legs. I save the bones when we eat the cooked serving pieces. I put this in a large crock pot with carrots, celery, onion, garlic, and herbs (whichever you wish). Then I top it off with water. I cook that on low overnight (usually around 20 hours but 12 is enough). I get around six pints of broth. I pick the meat off of those bones and use it in soup, chicken tacos, chicken salad, or on a sandwich.
This is time consuming, many people would never go to this much trouble but I consider it worth it. Many people would never cook an old hen because they don't know how to cook it.
Also do you find this changes based on breed if they aren't really dual purpose breeds?
Chicken is chicken. Dual purpose birds tend to have a lot more meat on them than the decorative breeds. Some people eat quail. Some people consider a decorative breed to be too small to fool with.
So much of this is just personal preference.
