The first part of the SWCP is well worth it from Minehead as far as Woolacombe but there is c. 14,000 feet of ascent (and descent!). However lovely views. The next part from Woolacombe to Westward Ho! is relatively flat 1500 feet ascent over 40 miles and then a bit "up and down" after that. I walked for a time with someone who wild camped and they didn't have much trouble finding somewhere, there is a lovely spot on the cliff top just short of Lynmouth - from memory about 1 or 2 miles from there. Navigation is no problem, keep the sea on your right-hand side!
I haven't walked Offa's Dyke but it looks pretty good as well.
Live each day like it's your last. One day, you'll get it right!