My Darth should be arriving tomorrow or Thursday. Others with three LED heads and three 18650 batteries in parallel are the new Solarstorm T3 and the FandyFire YL-U2 Warrior. I have the T3 and the Warrior so far and the T3 is brighter but the Warrior has a much warmer color temperature beam. All three are what I would refer to as skinny beer can lights. The SRK and M6 are fatter beer can lights, four 18650 batteries in parallel.
Based on listed dimensions the Darth is the most compact primarily due to having the smallest diameter head.
Based on the pictures in the above linked to review the Darth should be easy to modify as the driver chamber is readily accessible if you are a light modifier.