Yep. Definitely need terrain following for this one. Some good info is on this thread: 400 Acre site guidelines
DJI Pilot works okay for linear missions. On the R2A, the camera will control for overlap. Just watch out to make sure your trigger timing matches (from App to Sensor) to get an accurate front lap.
If you can provide a google earth area / line I can give you more thoughts… but until then, best of luck.