In 2019 I did a loop tour in and out of Halifax. I did not go to Newfoundland. I used my Thorn Nomad Mk II. I doubt that many things have changed, but since I was there before Covid, I would expect changes in lodging, campgrounds, and restaurants have occurred.
I did not stay at any hotels or motels. I stayed at an HI Hostel at the start and finish in Halifax. Also stayed at HI Hostels at the north end of Cape Breton Island and at Charlottetown, PEI. Everything else I did was camping. I was there for a bit over five weeks.
I am glad you numbered your questions, easier to answer.
1 - I do not know about mass transit options.
2 - I just made my own route with Google Maps and a general desire on where I wanted to wander. And I often deviated from my plans. Cabot Trail (highway, not a real trail) is a popular route, but that includes some serious hills.
3 - I mentioned Cabot Trail. Bay of Fundy has really big tides, not sure if that would be of interest to you.
4 - See first attached, the mosquitos were waiting outside my tent mosquito netting, waiting for me to unzip the door so they could come in for breakfast.
5 - I was there in Jun and early July. I try to beat the crowds, but later is probably good too. I want to be on my way home when the vacation crowds start approaching. Later likely is dryer. This is my go to favorite website to assess weather for planning my trips. I put in Halifax.
https://weatherspark.com/y/147454/Average-Weather-at-Halifax-Stanfield-International-Airport-Nova-Scotia-Canada-Year-RoundI think you get the best data if you put airports in the location search.
6 - I can only comment on Halifax. The Hostel I stayed at probably will not store your bike boxes unless something has changed, they had a small luggage room when I stayed there but the luggage I left there was pretty small. A bike shop named Cyclesmith offered to store my luggage for me when I contacted them by e-mail, I asked them if they could suggest a good motel that would be willing to store my luggage. In my case, I asked the hostel in advance by e-mail if they could store it for me. WHen I mentioned bike box, they did not read the rest of the e-mail, they said absolutely not. But when I stayed at the hostel, they told me that my luggage was small enough that they could store it. My luggage was an S&S Backpack case, which collapses quite small.
7 - I was mostly on lighter used highways, but I did ride on some rail trails on Cape Breton Island and on PEI.
8 - Whales, can't help on that.
Second attached is a map of my route.
Third attached, the steepest hill on Cape Breton Island. I pushed my bike up this hill, there was no way I was going to try to pedal up that thing. The sign says 13 percent grade. But it was only a couple km, so was not a trip ending problem, I knew about that hill from my pre planning before I got there.
Fourth attached, my bike.
Since I was camping and you would be looking for indoor sleeping, I can't really comment on where lodging may be difficult to find.