The parades start in Frontier land, go in front of the castle and down Main Street. Probably 15 minutes for them to complete that entire route. But if you are standing in one spot, the parade comes through and is over in about 2 minutes
Not sure I would call them parades. It’s just 2 or 3 floats with 3 or 4 characters on each. A cast member will come through about 2 minutes before and clear the path and then the floats will come through.
They happen all day long. Not really something you need to plan for and grab a spot ahead of time. You will see them happening throughout the day and can easily grab a spot on the side of the street and watch.