Virtual Shadow Map Performance

I test VSM in my own project , but the gpu shadow depth and shadow projection is not good ,shadow map is much better than VSM, I had converted most of staticmesh to Nanite ,Use Lumen , Disable static light just like Ancient Valley Demo , I find when i use VSM , a lot more “unaccounted” in stat gpu ,Can you give me some advice ? we really need more information about VSM.