I bought a T20 Q5 from Matt a couple of months ago. Works great on AW's protected (black label) RCR 123's. A little over an hour on high, about 2 hours 20 minutes on level 2. I use mine outdoors a lot, and there's a huge difference between level 1 (205 lumen) and level 2 (120 lumen). I guess if you're white wall hunting you may not notice a big difference, but outdoors you will. I'd like the low to be lower, with the new tactical lights, Olight's fixed that. I basically use mine as a 3 level light, 1, 2 and 5, so I can't really comment on the usefulness of 3 and 4.
After I set the light on Level 2 with 123 RCR's, I can then pop in a AW unprotected 17670 and it'll run for almost 2 hours. If you don't set it first, you may have to cycle it a half dozen times or so to get level 1 or 2, mostly it tries to run on 3 or it strobes. As the battery warms up it's easier to hit level 2. I have honed out the body so a protected AW 17670 fits, without the label. It fit before honing, but was way too tight. Now it slides in and out with little force. Very little honing was needed, there was only one part of the tube that was not concentric and now it is.
I've had several of the larger "pocket thrower's" and the T20 is the first one I've had that fits in any pocket of a standard pair of jeans.