You maybe right in this case and fully tuned the 650 could be the best or even a 500 might be better or maybe a 850 might be the fastest or even 1500+ cfm tunnel ram might be the quickest combo who knows, your making a broad assumption without much info/testing.
But what we do know in general 750 has proved itself as a good general purpose performance carb that has worked from stock to fairly wild. And generally a 650 is more than enough on the mild side.