Hello, if you don't want to opt for an excursion, renting a car could be a good option. It is quite easy to access the falls with public transit, for Sainte-Anne on the other hand, I wouldn't even think about it. If you go ahead with the rental, I believe this location is one of the closest to the port. Welcome to Quebec.
https://www.avis.ca/en/locations/ca/pq/quebec-city/qc3