You asked for comments by Canadians, I am from USA. But I assume you still want any info that anyone might have.
Last summer I toured for five weeks, starting in Halifax and finishing back at Halifax where I flew in and out of. A general comment, it was wet when I was there. I usually try to beat the traffic so i try to start and finish my tours before the middle of the tourist season. I was there in June and early July, perhaps it is drier later. A quick note on Halifax, I stayed at the HI Hostel there which was quite convenient. And Cyclesmith bike shop was VERY helpful. That said, I suspect hostels are not the best place to stay during a pandemic.
I did not make any reservations for campgrounds and did not have any problems. But several people told me that if I did not have reservations for Canada Day weekend, I would not have a place to stay. Looking at the forecast, I saw a lot rain around that time and the Hostel in Charlottetown PEI had availability so I stayed there for three nights over Canada Day weekend to sit out the middle of six consecutive days of rain. When I was at Five Islands Provincial Park on Bay of Fundy, almost every site was taken, that was in July. My point is that if you are there during busy season, you might need to make reservations if you are staying at campgrounds. In June, many campgrounds had a lot of room.
Some but not all Provincial Parks in NS have walk in sites. These sites are farther from the RVs and a bit more secluded, I stayed in those sites whenever I could.
I got lucky and had a walk in site at Five Islands campground for two nights. Great view of Bay of Fundy.
It can be quite buggy. Bring repellent.
When i was on Cabot Trail for scenic parts, it was foggy and rainy, thus did not see much. You might be more lucky.
There was one hill on Cabot Trail on the north end in the National Park, I do not recall which but it was a tall one at 13 percent grade. I pushed my bike up it.
Crossing the bridge to Cape Breton Island looks scary, but it is not that bad. Only the bridge portion has no shoulder to ride on, the causeway had a shoulder. So you are in the traffic lane for only a short portion, I waited until I saw no traffic coming before I crossed the bridge. Sorry, not a good photo.
I had 57mm wide tires, so I often rode on the gravel bike trails instead of roads when I had a choice. Since the bike trails often were flatter having been rail road grades, it was less hilly than the roads. PEI had very good gravel trails. This was the only spot where I had any problem on the trail, the downfall was quite recent.
There is a ferry and a bridge to PEI. I rode the ferry to PEI, then back to mainland on the bridge. You can't ride across the bridge, you have to take a shuttle.
This is the route that I took, it is my GPS track overlain on satellite map on Google Earth. The numbered spots on it are the dates when I stayed there in YYMMDD format, if I stayed multiple nights only the first night is listed.
I am retired and had plenty of time, so I took it slow an easy. Thus you will see I only had a few really long distance days, but I was there to enjoy it without any distance goals.
My go-to meal when I paid someone else to do my cooking was fish and chips.
The Propeller Double IPA was very good.
And occasionally had to stop for one of these.
