An important generality about the difference between cooking modern meat line chickens and cooking historic breed chickens is that for the latter there is a bigger distinction in time needed to cook the light and dark meat. Modern meat line chickens, being all butchered within a very young age range, all have leg meat nearly as tender as the breast meat, which will cook about as fast. The historic breed chicken has had more exercise over a longer time before it is butchered, which greatly increases flavor but also increases cooking time for those muscles. This becomes noticeable in the fryer age range: the breast meat of a fryer will reach optimal doneness noticeably before the legs. The difference increases as the butchering age increases, and seems pronounced in birds over one year. The cook has to plan how to prevent the breast meat from getting overcooked, and dry, by the time the leg meat is done. Good cooks will find many ways to achieve this end, and the results are well worthwhile.
I usually cook mixed pieces instead of a whole chicken. I like dark mean and DH likes white meat. I put the dark me on to cook 15-20 minutes before adding the white meat to have it all done at the same time. I like my dark meat done really, really well. I don't like to see the red next to the bone that happens sometimes when the meat isn't cooked long enough.
I don't usually have a problem when roasting a turkey. It is usually all done and not dry. But then, I don't eat the white meat, so I don't care if it's dry. LOL Bad, Bad wife!