North of Superior can be a little iffy based on the distances between gas stations. But generally, not a problem.
Their is one gas station between Sault Ste. Marie and Wawa, it's a tourist trap and gas is expensive there. Fill up either in Wawa or SSM.
Between Wawa and Thunder Bay, you can get gas in just about any town during 'normal hours'. White River (home of Winnie the Pooh!), Marathon, Terrace Bay, Schrieber & Nipigon.
Do NOT run over Superior after dark!
It can get a bit chilly/wet on that route. Make sure you geared for it.
Camping in provincial parks can get spendy in Canada. ($25-45/night). However, if you don't need a shower/electricity, you can legally camp on Crown land free gratis. Over top of Superior, see a lake you like? Find some access to it (nearly all do), set up your tent and done.
Otherwise, it's spectacular scenery. Recommend the Rainbow Falls campground, great sandy beach and great views.
As you can see from the pic, it's gets a little haywire on a Canada Day long weekend