There are two (by my standards) fairly meaty climbs on the route from Paignton to Exeter...
if you then picked up the Exmouth Exodus route from Woodbury (near Exeter) it's a flattish route but features Cheddar Gorge.
More main roads would be quicker and more rolling, but obviously nothing like as nice.
You could always ride from Paignton to Tiverton or Taunton and then get the train the rest of the way?