Maybe consult the vendor who supplied the carb? This is one of the common drawbacks of Chinese running gear, i.e. lack of tech support.
I get the impression that you know your way around a carburetor so, next best method is determining the float height spec the old-school way...lower it 2-3mm and see if the overflow stops. If not, repeat the process. Unless the float contacts the carb body, you shouldn't have to tweak the level setting very much.
One caveat...you could have a leaky float. It's not super common but, it does happen. Remove the float unit and shake it, listening for the sound of liquid sloshing around inside. If you want to be extra thorough, place the float in the freezer to get it good and cold, then hold it submerged in hot (130-140F) water, looking for small air bubbles as the air trapped inside the floats expands.