In phpinfo, there is a list of directives but they are not changing at all
I see XCache is there by 'php -v'
But how can I monitor the caching? Like how many scripts are cached or how much space/memory it used?
You can use the default xcache admin page to get statistics and details on cached objects.
Please read the official HOW-TO.
You could either write your own script using XCache API.