On our outbound flight, 1a appeared available at T-72 but got the error message on trying to take it. It opened up at check in T-24. Perhaps this was because 1K was already taken?
For our return 1a/k have just opened up at T-72 and I have been able to select them.

I think row 2 is better than row 3 regardless of side as it feels more spacious (assuming 747)