It’s extremely effective. 50-100 mL/bbl, depending on level of haze (which essentially just means gravity in beers that aren’t dry-hopped) and desired clarity, seems to be the sweet spot in my beers. As was mentioned, the cause of haze is also relevant - SiO2 is very effective against polyphenol (chill) haze but only minimally effective against yeast. I personally don’t find that to be an issue following an effective cold crash, but strain selection comes into play there as well.
I posted a photo in another thread recently of a 13-day old APA (more to the point, 48 hours after kegging): https://www.homebrewersassociation.org/forum/index.php?topic=24900.msg318812#msg318812 This was 50 mL/bbl (0.4 mL/L) BioFine A3 along with Whirfloc in the kettle.
FWIW, that’s what “cold crashing” means to me, though I’d prefer to go 48 hours. With any finings getting them uniformly distributed is essential. Fortunately, for a 5 gal keg that just means shaking it.