Wing it in Calabria Mid September

I would imagine you'd be fine; Tropean might be the most problematic but if you are not set on a particular lodging, I think you'd be fine.... I did travel there in September but I did book ahead....but I was only north of Lamezia.

These days, I would never wing it for a hotel, unless I wasn't at all picky. You can just waste so much time finding something.
If you want to remain flexible, book somewhere with short notice cancellation, so you can change if necessary.

These days you can book a hotel room from your phone while you're riding in a car or on a train. I think you'll be just fine. Mid September is starting to slow down, but especially towards the end of September there are lots of options if you're flexible. We've found massive discounts booking rooms at slack times if you're within a couple days of your lodging. Some innkeepers close up Nov 1 so this might be the sweet spot for you.

Calabria will not be busy mid-September because Italian schools will be back in and the area does not attract a vast amount of foreign tourism

All great feedback Thank you everyone
Lorie