Personally (and YMMV - I am a short arse) I would pick an aisle seat even if there’s others in the row. Middle sucks on long haul. Aisle means you can put your feet out a bit and get up and stretch anytime. Seats can fill up and change at the last minute. And if there are empty seats near you you can move. Just wait until after take off and give a nod to the flight staff to check it’s ok