You're trying to cram a lot into two or three weeks. I spent two weeks in Newfoundland last year and I didn't even get off the Avalon Peninsula, which is just a tiny portion of Newfoundland on the east coast. Gros Morne National Park justifies a week to itself.
Quebec City justifies several days. I spent two weeks there in 2000, although we did some day trips to Ile d'Orleans and Ile aux Coudres (both well worth visiting). There is spectacular scenery down the St. Lawrence Valley in Saguenay (fjords for example) but we didn't have time to go that far.
Newfoundland is accessible by ferry - but it's an 18-hour ferry ride from Sydney, Nova Scotia to Argentia, Newfoundland and then two hours to St. John's (which needs a week or more itself), or if you take the ferry to Port aux Basques, on the west end of the island (about 12 hours from Sydney, NS) you need about 8 hours to drive to St. John's.
In 3 weeks you could do Quebec City, Saguenay, and into New Brunswick. You might even have time for a few days in Prince Edward Island. You will certainly get some of your fishing villages there. The most stereotypical ones are in Nova Scotia and Newfoundland & Labrador, but that is (in my opinion) getting too far afield.
I've lived in Canada for 42 years and I still haven't been to all the provinces (NB & PEI this June, NS next May and I'll have the complete set!). Don't get overtaken by the need to do it all at once. It's 7,000 km coast to coast east to west and north to south.