I walked the St Ives-Pendeen stretch a few years ago as two walks, each starting from Zennor, and didn't find it the challenge I was expecting. At one point there were some boulders to scramble over but it was easy to do so.
I was lucky with the weather. This stretch is rugged and exposed and wouldn't have been much fun in driving rain. But it's a great walk, very scenic and with a feeling of remoteness.