Credit card/cash questions for travel in Canada

Look for a Visa or MC that has no foreign transaction fees. CU's often issue these. No, Discover is not widely accepted. Canadians use chipped cards with a PIN. We don't have PINs yet, but we will. However non-chipped cards are accepted.
Yes getting cash back is better if you don't need a lot of cash. Be sure you notify your CC company that you will be traveling and when or you will find your cards will not work, or will work one time and then be cut off.