Been on this aircraft twice recently (EWR-CDG & return) and think Row 7 is the best row in J, either the middle two seats for a couple, or side seats if alone. This assumes you don't need the larger footwell in row 1.

On both flights, Row 7 was the start of a virtual "second cabin," so that we got served the same time as Row 1. Being mid-cabin, people ahead of us tended to use the lav in front while those behind us tended to use the lav in the back. And we didn't have the issue with noisy crew in the front or back galley. As so reasonably good service and quiet flight experience.

Row 5 would likely be one of the worst for a single seat, given you're among the last to be served and you're missing a window, unless you're planning to sleep the whole flight and just want the privacy of a "straight" seat.