Malkoff has a bunch of drop-in modules that fit in P60 type flashlights like surefire 6P and so on.
such as M61, M61 "Low", et cetera.
The Hound Dog is a deviation from the standard and he reaches for performance, not comforming to the pre-existing standard. So you have to buy your own MD4 body or the entire lite from him. It's a very nice device but proprietory technology AFAIK.
If you require "two outputs and maximum around 500 Lumens", you don't want the M61** family, you want the Malkoff MD* stuff that can generate, e.g. the "HOT" module.
the "HOT" needs its own head, not a P60 bezel as far as I know and mounts to the MD4 body.
I would just probably skip all the intermediate models and go directly for the Hound Dog, or maybe Wildcat, but they are not exactly EDC material.
I would suggest getting a low model for a cheap Surefire 6P, you can get them for 20-30 tokens and then installing maybe Malkoff M61LL in it for every day carry but for ultimate lumens, get the Hound Dog, if the finances allow multiple devices.
This is IMO and there are about one thousand one of them on this site.