Which of these dogs sounds best for me?

If you can only give your dog one 20 minute walk once a day, than none of these breeds are for you. Even a chihuahua needs more exercise than that. Without proper exercise they will go crazy! I don't recommend any of them. The are all very stong willed. And have very stong bites... Not good with a 12 year old and small animals.The Presa Canario could be a real problem. They are extremely powerful and need a lot of training, not just the basics. The Wolf Hybrid will have a strong prey drive because it's so closely related to its wild ancestors. That means your chinchilla and cats will be dinner. If you want a big dog, why not go to your shelter and get a lab or a shepard? They should be easier to handle. And they do have purebreds at shelters. If you adopt, you're saving several lives. The one you adopt, the one who takes his place, and the fee provides medical care to other animals.