Have just flown LHR-LAX on a 787-9. Only 28 passengers on the entire plane, including 3 in F. My wife and I chose 1A & 2A. Because onboard service is currently much reduced it was difficult to tell which side of the plane is best. The forward galley was hardly used (prepared food already packaged on trays) and the attendants didn't congregate in it. The one lavatory is on the left side, and most of the crew traffic also seemed to be on this side. So, on balance, I think I should have gone for 1K & 2K.

Unlike the 747 in which the window seats have much more space than the middle pairs, the 787-9 has more cramped areas, so possibly the middle seats would be better for pairs of folks. Not much difference in truth. Pretty crammed in relative to the 747 and 388. And downright poor compared to Cathay, Qantas and Qatar.

The flight crew didn't have much to do, but what they did was done with grace and charm, if lacking efficiency.