Q: Should "Global Config Statistics" be enabled?
A: We recommend you turn off Joomla's default statistics as the JoomlaStats component is much more powerfull. By turning off the default statistics this will also improve the page load times.
However you may keep the default Joomla statistics collection turned on, and have both (default Joomla and JoomlaStats) collect the statistics. They won't interfere with each other.