Pause Eevee rendering - speed up EeVee render

Does anyone know how to pause EeVee render that current set with FFmpeg output format?
Also does no. of polygons (mesh with lots of vertices) slow down rendering even not within the view of the camera?
I understand for “cycle” we can do ctrl-B to limit the area of processing. But is that possible too on eeVee?
At the moment, I have a very large scenes with many objects and animation … and like to see how to speed up rendering.

Hi … closed. Found the answer …

Use “Esc” key or click “x” on “render result” window.

To have partial render in EeVee (same as cycle apparently), based on only Camera view, you can define a Render Region by menu View → View Regions → Render Region… You can also define a Render Region in any other point of view to use it for Rendered Display mode.