A food-and-coffee day in Penzance works best when you treat it as a slow wander rather than a strict trail. The town and harbour area lend themselves to that kind of browsing.
Mix one or two planned stops with a bit of improvisation so you can choose a place that matches your mood rather than locking everything in advance. Chapel Street, the harbour and nearby side streets all suit that approach.
If you like local food guides, Penzance is at its best when the day includes at least one proper sit-down break and a little time to look around between stops. That is how the place feels most like itself.