95% of the time I fly alone, so have not really bothered with TS or blocked seating in the past...
Recently qualified as Gold for the first time

In Feb I have a flight to Malaga in ET, with a friend on the same booking, me gold him blue.

If I select two seats in an exit row on a 320, for example 12A and 12C, would 12B be blocked and we would be 99% sure of having an empty seat between us, unless the flight is full. Because people don't usually select middle seats when travelling solo. ...

Or are we better picking 12B and 12C to guarantee sitting next to each other and 12A would be blocked until check in?