Coming back to this thread...my experience with my 3590s and the 1750mA driver is that it was a little overkill and a 1400mA driver would likely have served me (almost as) well. "Overkill" because back then we I had the light built some months ago the HLG 240W 1750mA driver was rare and barely available, more expensive etc.... it was more like I wanted the "best of the best" so I insisted on the 1750mA driver. It is my understanding those COBs run most efficiently at about 50W, if you run them at 1750mA you get (of course) more light, but 63W is a little less efficient. For some this could be a criterion. That being said I am happy with my lights. I am of course only running them at full power when I am flowering, even dimmed down (with the internal dimmer) to 850mA this is a ****ton of light for vegging, 550 something PPFD for my area. Doesn't get any dimmer.
As for penetration...it is my understanding that lenses are very beneficial there if you want to max out penetration.
Edit: No, I wouldn't want to buy a "cheap" LED driver from ebay, unless some reputable guy on the forum would vouch for a particular vendor. Greenhouse = wet, dusty, humid, fire hazard, lamp is DIY lamp with
Edit2: I would be careful buying a "cheap" driver off ebay etc...greenhouse is humid, wet, dusty etc...not something where I'd want to risk anything with low quality components.
If someone would sell the MW drivers for $40 I'd be VERY wary