How it works?

Hi guys! I stand before the election of components for 10 pc in my studio and I’m worried about the question of how to pick up the components that would not be lost in the price / performance ratio.
How does Blender work? I mean, how does everything go between the devices, data exchange, what is being recorded? For example, on what depends how many polyons does the viewport hold during sculpting? Why does it start to slow down the viewport when you twist the model? What part does RAM, processor and video card take?