I've not done that section, but have done parts of the SWC path (Plymouth heading West), with backpack and wild camping.
Backpacking is fine, though it's amazing how the constant up and down takes it's toll on your knees - far more than any hill walking I've ever done.
Wild camping isn't easy. It took us a long time to find a pitch each night for the reasons Wurz mentioned, though we did manage it. Finding water was harder, so top up at every opportunity.
After our last night someone told us that lots of people wild camp on the beaches, which we avoided because we weren't sure of the high tide level. If you can do that it makes wild camping much more viable.
Or, identify some farms along the route and ask permission. I believe the SWC path association can help with that, and may even have a list.
Here's pictures of my three pitches on the path:
Mark