Rhode Trip - that is essentially the route I took as well. We did it in late June, and the ferries were EMPTY. We had made reservations, and sleeping berths, but there were less than 100 people on board. It was nice, but kind of spooky. I should put up a webpage about the trip one of these days.
We were surprised to find some parks closed in Nova Scotia, as they use July 1 as an opening date. We spent a day at Louisborg, which was impressive.
http://fortress.uccb.ns.ca/
Once in Gros Morne, we camped a few nights at Trout River in a Parks Canada site, and only three other cars were there. The showers were HOT, and so clean - they really exceeded our expectations. There was a fellow van camping on a sweet overlook near Trout River.
Enroute north, in Labrador, we spent 3 nights at Battle Harbour, a Labrador island, which was fantastic. No bugs!
http://www.battleharbour.com/home/
The Trans-lab does have many places you could pull over and camp. No problems there. We chose to push through to Lab City and get a hotel, as that was a rainy stretch for us. It seemed legal to throw down a roadside camp wherever you wanted in NF and Labrador. I did see a few trucks set-up in gravel pits, not exactly scenic. Not many choices off the roadside - it's all bog, Canadian Shield, wetlands - not many dry, open prairie fields like you may find in the midwest.
We did not see any whales, although we're told it is common on the Blanc Sabon ferry. No icebergs either - a sign of the times.
The Walmarts took us by surprise - dissapointing. Fermont is worth exploring. The scale of the strip mining is staggering. Tim Hortons becomes a welcome lifeline. The manic 5 hydro series is great, and that road is neat - I gotta go back on my motorcycle from the St Lawrence north, what a great stretch of twisty pavement.
We returned via Baie Comeau, which we did not have a reservation on because we really didn't know what day we would exit. We made the ferry on stand-by, but barely. Then we spent a day traversing the Gaspe on dirt roads, along the International Appalachian Trail, which was also great fun. Gotta go back there as well.
Met a few guys on dual sport motorcycles doing the loop, and a few on bicycle. That is a hard pitch - I have no desire to pedal my way across the Trans-Lab, but more power to them.