1) those who segregate more, if anything, have less of a shidduch problem. Think chassidim.
I’m not sure that you can attribute the “ease” of marriage among chassidim to greater gender separation.
I think it’s far more attributable to the fact that the chosson/kallah have very little input into the process — something that does not apply to the rest of the Jewish world.
However, if you compare like situations (i.e. ones where the chosson and kallah are the primary decision makers and not the parents), I’m not so sure that your rule would apply.
The Wolf