Yea, I have a few similar drivers from 18w LED tubes(1$, e3ay), uninsulated and they also claim 91% effiency and power factor above 0,9 in their describtion. 80v/240mA max. but unfortunately not dimmable.
I think I'd use them for 2 or 3 BLX Vesta strips (one for each color channel). So I could use them for my living room and use either 5000k, 2700k or both channels together depending on the time of day. But I do not like the solution yet! For my living room I actually want something dimmable, you know, both channels steplessly dimmable so I can mix both spectrums individually. I can not achieve that with these drivers. Although there are dimmable tube drivers(dali) out there, but not for just 1buck like this.
At least they seem to use better chips now in this little tube drivers and have significantly improved the efficiency.
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I can easily imagine how a 2nd bar like this could be used in flowering when you switch to a 12/12h light regime.
One bar for veg = 18h with up to 128w and two bars for flowering =12h x 256w.
Assuming 140lm/w are ~2,0μMol/j you have ~ 250μMol/s PPF from one bar, or around 500μMol/s/m² PPFD on your 0,5m². (40x 20")
With two it would be already around 1000μMol/s/m².. of course with the usually used 10-20% less it's only around 800-900μMol/s/m², but that's just the amount of light the most growers are looking for.