What each client does
v2rayN is an open-source GUI client for desktop systems, with tools for server management, subscription groups, routing, and proxy settings. v2rayNG is for Android, uses the Xray core, and integrates with the system VPN interface. v2flyNG is also for Android and uses the V2Fly core; consider it when you specifically need that core. These clients turn user settings into network configuration; they don't provide server services.