Actually, I was referring to ordinary outdoor
LED floodlights.
While still not perfect, the lumens output is far more important that the watts consumed. That bulb you linked to puts out 700 lumens.
THIS Cree lamp puts out 1500 lumens, yet only consumes 23% of the electricity.
Back to your lamp holder, you're going to have a very tough time supplying enough light, no matter what bulb you use, from those distances. You might get away with very low-light plants at the 20" distance, but the current limitation of the fixture will prevent you from having a meaningful light source at those other distances.
Don't forget the inverse-square rule!