I found and fixed the cause of the cubemap seams in variance shadow maps so we now have nice soft seamless shadows.

I also changed the engine so that point lights use six 2D textures instead of a separate cubemap texture array. This means that all light types are sharing one big 2D array texture, and it frees up one texture slot. I am not sure if I want to have a hard limit on number of shadow-casting lights in the scene, or if I want to implement a system that moves lights in and out of a fixed number of shadowmap slots.