There should not be a performance impact because it comes from Datasmith. At the end of the day, whatever way your asset came into the scene, the engine is managing meshes with material slots and lighting configuration.
Many things can impact the frame rates:
- draw calls: how many distinct meshes are used by actors (are you using instancing as much as possible), how many materials and material slot per meshes.
- number of triangles: are you LoDing or using nanite.
- complexity of materials, lighting and graphical effects you set up in your scene
- etc.
We would need more details on how your scenes are built.