Viewport rendering renders a viewable screen.
It is similar to screen capture. 
Of course, it will be rendered to the desired resolution.
A camera is required to use the rendering engine in the blender.
However, viewport rendering can be rendered without a camera.
If you want to render using a rendering engine, use Addon, which allows you to install multiple cameras and manage them.
This Addon is for camera management. (Free)
It works, but it hasn’t been managed for a long time, so some features are problematic.
This is not related to rendering quality.
Add…
The method of installing the camera on the desired view screen is Alt+C key.
The way to set the existing camera to the view you are currently viewing is Ctrl+Alt+ numeric keypad 0 after selecting the camera from the outliner.