I think one is totally able to do a tour of these medieval villages independently. (I am assuming this is your trip in November you were posting about a few days ago?) It may be a bit chilly then (hovering around 10°C), but the weather itself shouldn’t interfere in your sightseeing experience.
I have not taken a tour, but I would suspect that there are pros and cons for doing it on your own. Without a guide, it may be a bit difficult to gain a good sense of the history and context of these villages and ask questions, if I recall there are not many information plaques around these villages, one will have to mange with a guidebook. On the other hand, going independently will allow you to go at your own pace and visit the villages you specifically want to see.
Another concern will be parking, however most of these villages have some form of larger parking area just outside or around the village, so it will probably not be much of a worry in November.
Staring in Barcelona, I would do something like this:
Besalú
Castellfollit de la Roca
Rupit: (my favorite) for a nice lunch, stop here at Restaurant Albert for a view of the village below and hardy Catalan mountain cuisine.
Sant Pere de Casserres: a clifftop 11th-century Benedictine monastery overlooking the Ter river. The monastery also has a small exhibit depicting medieval monastic life.
Return to Barcelona
Closer to the Costa Brava there is another smaller medieval village that may be worth checking out too called Pals, but it is a bit far away from the other ones, which is why I left it off my proposed itinerary.