I can touch on the Northern Canada part a bit! A lot of the airports you are referring to will indeed have commercial traffic flying in, but not usually busy enough to cause any conflicts, except the odd occasion. Some may only have an arrival every couple of hours.
The busier airports will tend to have a Flight Service Specialist (FSS) who provides advisory information to VFR and IFR aircraft to allow for separation and avoid circuit conflicts. Typically in the form of extending downwind, upwind, etc. However, this is only an advisory service, and therefore still uncontrolled.
For areas that are very busy, even in Northern Canada you will get a control tower. On the contrary, for those airports that have neither an ATC or FSS, it all comes down to good airmanship. VFR established in the pattern have right of way over IFR traffic on an approach in VFR weather (in IFR weather, there should hopefully be no VFR traffic). However, good airmanship, would have a small C172 doing circuits, extend a downwind slightly to accommodate a CRJ or Q400 landing straight in, even if the C172 technically has the right of way!