Have a look at Sustrans for traffic free but a lot of road roads are very very hilly……..
We’ve done the below cycle ways so if you wanted to car about and cycle but they’d be out and b@cks but you could overnight as a couple are a bit longer
Camel Trail, as in your hol link, is lovely esp into padstow
See also Tarka trail *n Devon from Braunton etc, some nice costal bits
See drakes trail , Plymouth n to Dartmoor so could probably add a bit
See granite trail okehampton, Ledford I think
See mineral tramways deveron to portreath (can chuck in ferry rides to Truro)
See https://cycle.travel/route/devon_c2c