I can't see the detail enough on your Ontario part to comment but I rode from Kitchener up to Elliot Lake a few years ago. I drive up there often enough too and highway 17 in that part of the province is just a terrible ride. and would recommend you ride across southern Ontario and up the Bruce Peninsula, take the Chi-Cheemaun ferry and spend a few days riding around Manitoulin, it's only got one stop light and no fast food type places, one of the nicest parts of the province if you ask me. Toronto and the area, the GTA isn't really all that nice to ride through and unless you have to see the big city it's totally skippable... you could also grab a hotel near the Barrie GO (Ontario commuter train service) station and take the train into the city if you wanted to see some of the sights and save yourself the hassle of riding in the traffic. The best touring around Toronto is to be had slightly north of the city, crossing the Niagara escarpement and checking out some of the sights and hills. I recommend the forks of the credit and the various little "badlands" around Mono. If you're not really into hills or wanted to take it easy for a day there is a decent rail trail that runs from around Shelburn all the way to Owen Sound, it runs parallel to highway 10 for the most part so you can always head off the trail if it gets boring. Riding up on the Bruce is super nice, and there is a beautiful side road on the east side that is really quiet and has some quaint campground along the way too. The aptly named 40 hills road is gravel but I made it through with 32mm tires no problem.

I can't comment on the eastern part of the province or the far north but I rode from Manitoulin up to Espanola and then across on Lee Valley Road, it cuts off ~40km of riding on highway 17 and you can duck down on River Road or something like that and shave off another 15 or 20. Highway 17 has no shoulders and a 90km/h speed limit and there's a lot of truck traffic so it's not really all that fun to ride but lots of people do it. I haven't personally ridden much past Elliot Lake on highway 108 but it's quite scenic. If you were into doing the wilderness thing you could take 108 north until it turns into 546 and then get on the 129 and ride up to Chapleau and then across to Wawa thus saving you a few days of riding on highway 17 but there isn't really much of anything along that way except for a few hunting lodges so you'd have to be sufficient enough to do ~250km without any real big towns or anything like that. The roads are pretty lonely too except for the occasional lumber hauling truck. Lots of bugs in the summer too.

Here's some maps to help illustrate what I'm talking about, the first shows Manitoulin and some nice sights to see. The second is my preferred option of riding the Niagara escarpment but the hills can be kinda steep since the roads all run straight on a grid system, mostly. The third map shows the rail trail option and avoiding the more scenic escarpment in favour of an easier ride. Most of the main roads in Ontario don't have shoulders but since the province in the southwest is all laid out on a grid one can usually by-pass most busy highways by criss-crossing the concession roads.