Actually no, what I just said is incorrect, it’s the other way around: non-HDR lighting should’ve become darker. Still, your pictures with the new VXGI look way too bright, multibounce shouldn’t affect the result like that.
I realize that the shadow is created by a distance field, so you want to replace the light with an emissive surface and get shadows from VXGI? It’s technically possible to get a more or less correct shadow, we could trace cones toward a specific area light, but that would be expensive and that is not implemented in UE4. Getting VXGI shadows from a regular light is not possible.