What rain drop particles? Do you mean the fast moving gpu particles with occasional highlights in the air?
As for the ground its way too dark to really see what is happening, but the illusion is sold by lots of moving little debris on the ground as well as a reflective ripple shader coat, and the mist particle effect intersecting the ground with a gradient giving the illusion of moving tiny water particles, I think there may be some particle tiny ripple effect done through shader. If you want to take it a step further I would bake one Alembic mesh sim of particles splashing with wind from 3d package and import them as scattered particles with random rotation varioation on the ground to sell the effect further but that’s overkill.
You wont see anything this good in Epic examples because Epic is not trying to make a product like this, they are just average examples and again it is mostly the lighting and composition selling this scene, he is also using Vico dynamics for the wires, I thought he prebaked those but could work both ways. It is all about cheating and making a scene work, If you break it down in full lit daylight (if it is ever posted ) perhaps you will see what I mean.