It doesn't matter whether it is 500 or 2000 out of box. User should be aware of this limit (150) before they install it. Any new request over the 150 (even though max connection settings is higher) limit will be queued until backlog is full. On the other hand, the backlog queue (has nothing to do with 150 limit) would not be flooded as pointed out earlier. anything above the limit will be dropped.
If you have a higher traffic site, you should use Enterprise Edition.