I'm sorry, but the knowledge sources provided do not contain specific information about how the Mixpanel script affects Google Page Insights or page speed scores. The documentation covers how to install and configure the Mixpanel JavaScript SDK, its features (like autocapture and page view tracking), and comparisons with other analytics tools, but it does not address the impact on website performance metrics such as those measured by Google Page Insights.
If you need detailed information on this topic, you may want to consult Mixpanel's support or conduct performance testing with and without the Mixpanel script to observe any differences.