I don't own this laptop anymore, and now I have a ASUS which with a mux switch, a more beefy Intel UHD and also a more powerfull NVIDIA dGPU so, these metrics might not be true anymore and disabling the NVIDIA Gpu will bring battery gains. Intel iGPUs got to a point where they can handle pretty much the modern web animations of today.
PRIME is a technology used to manage hybrid graphics. It was meant to be a resource saver since you can configure it to use only the Integrated GPU, and render offload to the dedicated GPU whenever is needed. But that is not what happened in my real life situation.