Pretty certain PWM - but I'm not an expert by any means. Can't recall if it's made obvious on website anywhere.
I think PWM is consistent with the explanation "driving methods of LED module" in the data sheet at bottom of page 3
http://www.meanwell.com/search/LPF-60D/LPF-60D-spec.pdf
I think the driver has controls dimming with stepped outputs - dimming at low levels 10-20/30% don't ignite the V18. When over 30% sweeping the trimprot increases brightness in noticeable +10% steps
At 100% output in 220V driver is producing 6W of heat. In practice I'm at ~52W I'm finding the drivers each put out as much heat as the 12Vdc wall-wart which powers my 3 computer fans.
Over last few days I'm seeing some new light damage on leaves and diminished growth at 100% output (105W iirc). Not sure if this is caused by switch, or substandard grow. Back down to 50% (52W) for now.