How does one create this effect and be able to control the level of dithering?
For Eevee, the principle is similar to the one used in this answer.
Simply you can change the input parameters and play with the Voronoi texture options.
I've changed few things to the node setting.
Voronoi input is set to camera texture coordinates.
Voronoi changed to 2D and distance to edge.
Inputs on the right tuned.