I've only used my billows once with the 2" screw adapter on my large LSG once, but it held temps pretty evenly compared to my first cook. I will say it was better than valve alone, which I used for my first seasoning then first cook. The biggest difference was on the recovery from when I would open to mop meat and cool February Florida weather. I had to open the valve 50% after closing to bring temp back up, then close back down once getting close after 15mins or so, just before moping again. Didn't have to do that with the fan.
Full disclosure, I used lump charcoal the first two cooks and the valve, briquettes with the fan. Didn't like the flavor of the briqs, so going to try lump again with Texans fan and open top technique on youtube. I ran my Saffire kamado a lot like that with bottom air feed barely open but top nearly fully open (exhaust "cap" rotated closed but vents on the cap were all the way open for 300F temp) and that made a positive effect on flavor, so ran it that way for years when I had it.
