There is no barrier between Comfort+ and Economy in the A330-900neo. Someone will be directly behind you. Here's a good map of what the plane looks like: https://www.aerolopa.com/dl-339

I would avoid the front (bulkhead) row 30, which I personally hate sitting in because of the requirement to stow my bag overhead during takeoff/landing and the fact that I can't stretch my legs out. I generally avoid the middle group of 4 seats and stick towards the sides of the plane, but I also generally sit at the window for long-haul flights so I can catch some sleep.