General
The General settings tab (under Settings in the sidebar) holds the site-wide configuration that affects every published page: title, description, language, base URL, home mode, performance mode.
Performance
The Performance section in /settings/general controls how the admin queries the posts collection in Firestore. There's one toggle and it has real implications for sites with thousands of posts.
Plugin settings
Each enabled plugin can declare a settings page reachable at /settings/plugin/. The Settings sidebar lists every such page in a tab strip alongside General + Performance.