I can't see how design number 2 could possibly be considered efficient with the frontal area of two fuselages, two/three wing/fuselage junctions and a centre wing box that is going to have to cope with a heck of a lot of torsional loads. Is it hydrogen powered? I can't think why else it would be that shape.
Bearfoil, I would say that the Mcdonnell XP-67 predates the F16 by a few years, and that's ignoring the various Hortens and such like which must also qualify as 'blended wings'.
