I'm Peter, the installation guy. I never considered using xf_ as a prefix, as it's default table names. vB
has the option where you can prefix tables, where no such thing exists on XenForo. Maybe it would be nice to add that to the documentation, or even better, auto-fill it in when XenForo is picked as the forum of choice?
As for the other settings, none of them seem remotely related to XenForo, so I'm not sure why you would call one setting "entriely too many things answered as n/a".