How to set the default statistics component for the new subscriptions?
It can be configured in in Service Plans. For example, to set AWStats as default component for all subscriptions that will be created under the Default Domain Service Plan:
1. Go to Plesk > Service Plans > Default Domain > Hosting Parameters > General Properties and set "AWstats" as it is shown on the image below
2. Click Update&Sync button
Note: AWStats will also be set for all existing subscriptions associated with this Service Plan