Here is a list of
online maps of Yellowstone which may be of help.
The Canyon Campground isn't too far from Yellowstone Canyon and the Falls, so walking to those sights may be practical. See the map for Canyon Village in the list above to get an estimate of the distances.
We have been to Yellowstone a number of times over the years and never camped at Grant Village. In our opinion it is just too far from the action. It is adjacent to Yellowstone Lake and the West Thumb Geyser Basin. In our past visits we never saw a geyser at West Thumb, just some hot springs. A day or two at Grant Village would be plenty to cover those sights on foot.
Something like 25% of the geysers in the world are at the Old Faithful area, along with many hot springs. The closest campground to this area is Madison, 16 miles away. There are other thermal areas, some with geysers, between Madison and Old Faithful. A bicycle would be a more reasonable method of travel between these areas.
The non-reservation campground at Norris is only a mile or so from the Norris Geyser Basin.
The non-reservation campground at Mammoth is within a reasonable walking distance (all uphill) to get to the Mammoth Hot Springs terraces.