Transportation: There are a number of different ways to get around Toronto. If you are on a budget, like I normally am, then the train and Uber are the two to use. The train takes twenty-five minutes from the Airport to Union Station, in Downtown Toronto. The cost is $12.35 for one way.
Luggage: If you are like me and only use a carry-on to travel, you are going to want to store your bags for your layover in Toronto. The Toronto airport does have a place you can do this at the Excess Baggage Company. I have not personally used this, but the prices seem reasonable. If your layover is overnight, some hotels downtown will hold your bags for free even after you check out.