A full-system emulator, like the virtual device in Android Studio, runs a real Android: complete system image, virtual machine, hardware acceleration. It's the only way to reproduce a WebView bug, test a native app, or an older version of Chrome. It's also several gigabytes to download and a minute to start, and it doesn't open in the middle of an integration session.
A browser Android emulator, on the other hand, is a simulator: it runs no system, it replicates the display conditions of a device in the browser you already have open. This is what Mobile FIRST does for 31 models from 9 manufacturers, with their viewport, density, User-Agent, and touch events, on Windows, macOS, or Linux.
The responsive mode of DevTools resizes the window and changes the User-Agent. It's an inspection tool: no device frame, one screen at a time, and nothing to show a client. Remote debugging via USB, however, is perfectly accurate — but it only covers the model you have on your desk.
The limitation of simulation is always the same, and it's better to know it: the rendering engine remains that of your browser. It covers layout, breakpoints, density, and touch behavior; for behavior specific to a manufacturer's WebView, a real device or emulator is still necessary.