I getting an Unused JS notice on Google PageSpeed Insights for analytics.js/gtag.js.

Google Analytics offers two code libraries: analytics.js and gtag.js. A library offers easy implementation of a certain application, but this wide compatibility range comes at a cost: it probably contains a bunch of code you don't even need.

If you are a light-weight Google Analytics user, you can enable Minimal Analytics in CAOS' Basic Settings: Settings > Optimize Google Analytics > Basic Settings > Snippet Type: Minimal Analytics.

Minimal Analytics is fully compatible with Stealth Mode.