How do you intend on fishing? Are you bringing any sort of watercraft? Relying on shore fishing? Charter/Rent?
In general, Southern Ontario (South and West of Barrie) is more big water fishing (Great Lakes) and some river fishing. Plenty of charter opportunities if that is what you are looking for (Salmon, Walleye, Small Mouth etc). Pretty hard to fish these waters on your own unless you are well equipped. Shore fishing/River fishing in Southern Ontario probably would be a little underwhelming for a fishing trip.
Central Ontario. North of Barrie, East to Ottawa and Up to Sudbury, is considered cottage country. Lots of smaller lakes, more manageable water, fishing is considered better in general. Should be easy to find good campgrounds, Wifi maybe, and boat rental/guides/help pretty easy.
Northern Ontario is north of Sudbury. Fishing is generally considered really good (Walleye, Pike, Trout) would be the species normally targeted. You probably won't find nearly as many serviced campgrounds, wifi probably limited. Fishing guides/boat rental would be primarily out of lodges.
Access to quality fishing is likely inversely related to the quality of RV campgrounds, unless you want to pay for charters on the big water of Southern Ontario.
