More information is needed.
When you talk about the lag or smoothness of the rendering, are you referring to dropped frames, are you refering to the consistency of the geometry, or the refresh rate of the geometry?
What are you doing with the old meshes?
Are you using CreateMeshSection multiple times every frame?
Are you sure that there is some lag between when the CreateMeshSection function is called, and when your geometry appears, or could it be due to something else, like garbage collection? Have you tried using UpdateMeshSection instead of CreateMeshSection?