I have always been drawn to the Coast whilst in Devon. I dont know whether you are north or south, but the coast path west of Clovelly towards the Cornish border is superb ( and tough ! ) In South Devon, the walk between Brixham and Dartmouth is really good , bearing in mind its proximity to Torbay and has good public transport. There are lots of other "good bits "-- try the South West Way association website for more details.
I have done some of the Two Moors way-- this can be started/ finished at Plymouth to give you a Coast to coast walk. I dont know much about the Tarka Trail-- except that its something to do with otters !