First of all, the author of the article stated that the "idle bleed" or something like that were adjustable. I could find nothing in any picture posted that would lay claim to that. If the author was talking about air/fuel mixture screws that a totally different thing.
Also, the air valve on the secondary isn't new either. Just exactly like a TQ/Qjet.
I'm never a fan of a restrictive booster design just to try and fix atomization. You can do that better ways. Like an annular booster, which can be restrictive, but not nearly as bad as what that Demon booster has.
As PRH already mentioned, there really isn't a way to clean up the idle circuit on that carb, without some serious work. I don't see any easily changes air bleeds either.
The last thing is they never dyno tested any other carbs against those carbs. How do we know if you dropped two Holley based carbs on there you would gain 30-40 HP and gain a bunch more tuneability?
The last thing I'd say is don't buy the carbs (any carb for that matter) based on advertised CFM numbers. They are essentially meaningless.
See if you can find out what the primary Venturi diameters are. Chose the carb by that rather than CFM. You don't have to worry about the secondary side because it doesn't have a Venturi like that.
It would seem to me the 625 carb would have to have a pretty big Venturi to get the air loss back from the restrictive booster.
And I never consider anything under 750 sized venturi's for any 2x4 application. I've lost power every single time I've used smaller carbs.
The only time that didn't happen was when everyone and their mother was in love with the 660 center squirter carb. IF You used an 850 base plate it got close to a 750 but even then, the tune up from Holley was atrocious.