Here's a stellar route for anyone who wants to avoid traffic and see the most unfrequented roads and tracks. So many variations of this route are possible, but there are certain unmissable sections like the tiny road linking Gaggio to Buglio that doesn't appear on most maps, or the pristine gravel across the bottom of the valley floor from Ere to Ardenno that gives such a sense of tranquility, so far removed from the madness of the main road.
Year-round route. Gets pretty muddy on the valley floor after rain. You can get away with narrower cyclo-cross tires on this route.