I've flown the A339 a couple of times, my favorite seat is the bulkhead because the footwell is bigger. I've never flown in the middle but from what I saw (and read online) the divider doesn't drop very low. If I were flying with my husband we would just sit in window seats.

On this plane it's the even rows that have the side table between the aisle and the seat (eg seat is closer to the window) but the odd rows have a slightly longer side table and a little cubby underneath the longer part.

Hope some of that helps.

Edited to add - I was not bothered by galley/bathroom activity sitting in 1J.