The muzzles are worn to protect the dogs from doing injury to each other when they are turned out en-masse or become excited during a race. They enjoy a brisk walk or a good run in a fenced area, but around the house they're usually 40-m.p.h. Like most sighthound breeds, they are quiet and relatively inactive when indoors. No, unless you get a dog that has already been in a home. They are crate-trained at the track, and very clean dogs in general.
Adult dogs have many distinct advantages over puppies.
Adults are also less active and better behaved than most puppies. I want a dog, but I'm not sure a greyhound is right for me. Read all the information you can find about choosing the right dog for you. Visit your local animal shelter and talk with the staff about the dogs they have available. Unfortunately, you can never be quite sure what you are getting.