if the vacuum is high than that at WOT the carb will flow more than it is rated for, if it's lower than that it will flow less than what it is rated at
Correct

To estimate engine vacuum: CFM = D × peak power RPM × VE (use 100% here for well developed heads and good cam choice) ÷ 3,456
572" × 7,000 × 100% ÷ 3,456 = 1,159 CFM
It will draw more than 1.5" Hg vacuum* from an 850 (and CFM will increase), and less from 2 × 750 (and CFM will drop off). Size is somewhat self-correcting.

* a carburetor much too small will not only increase WOT vacuum, if will do weird things to the mixture curve (too rich on top, but not necessarily linear), and may also trigger vacuum spark or close the secondaries.