it seems like there is a feature in blender to 'viewport render animation', but i don't think it's possible to render as fast as you are thinking, especially without losing some quality in many situations. further reading: https://blender.stackexchange.com/questions/124574/will-it-soon-be-possible-to-render-an-eevee-animation-in-realtime-2-8-beta
ah, that is the piece of the puzzle i've been missing