It is close to 8000 OTF lumens and near 500kcd in a 5000k/neutral from the de-domed xml2's . Not over keen on the 6500k generally . I can cope with cooler tints, but I prefer a more neutral given the choice. Heat wise it copes very well, many lights with 15,000lm or more are good for a minute not so, then you have to use at 50% or even 30% for any length of time . This you get full performance , yes it does get quite warm but manageable .
No it does not allow use of less cells/ leds unless you chose the rc40vnF version(this has 2 drivers that work 3 leds each of each button), it has a 6 cell propirotory pack which can be removed and swapped out for another if choose to buy a separate pack. Mine has had the cells swapped for 10a 3500mah making it a 10,500mah pack. If using the USB function it doubles to 21,000mah going off fenix specs (doubling iirc).