The grouping setting is, more or less, just a visual setting where results from the same domain are grouped together:
Disabling this effectively just makes every result a "top level" result like all the rest. Slightly more to it than that, but in short it does not affect the calls that we make to our upstream sources; just adjusts the presentation. So the overall volume of results will be the same either way.
No matter what your settings are, we generally always request the maximum amount of results we can get from all of our upstream sources in a single shot. Getting more results from any particular domain - or anything that implies "more results" than what we show now - requires doing another search (incurring more cost to us), so it's an explicit option.
