Iceland in 7 days without 4×4: realistic itinerary or continuous run?

We will leave in two at the beginning of September with a small normal car. The initial idea was to complete the whole Ring Road, but I see days with four or five hours of driving before the stops. We are interested in waterfalls, thermal baths, landscapes and short walks; we do not want to cross cheeks or run to put a flag on every place. I am evaluating south coast to Jökulsárlón and peninsula Snæfellsnes, giving up the north. I am interested in a comparison based on recent experiences: indicated travel period…