Actual watts vs light brightness

This is my second bp2000 the first was like 21.5x12 and stated a actual watt of 205 as stated on line and in the user manual with .5watts leds and worked great which led me to purchase another bp2000. The new one called an upgrade states an actual watt of 160 in the user guide but 205w online. The leds show .2watts and it's 18"x12" with a slightly larger driver and 1150 leds. The first bp2000 has 656 as stated online and in manual.

How much difference will the led chip size, the actual wattage, and the unit size make in a 4x4 tent? How crucial is the actual wattage in a grow compared to light brightness.

Wattage is a rule of thumb measurement for Led's, for example, you want apx. 35w led/sq ft. of grow space.
As far as advertised & actual wattage, I believe what's printed on the driver.

In my (slightly smaller) tent, I have 480w (dimmable) led, I use a cheap Lux meter to adjust the intensity.

Good luck