Here is a general rule of thumb you can go by:
- If a mesh is not important in your game, then set the RenderFidelity to Performance or Automatic.
- If a mesh is important to your game, consider setting the RenderFidelity to Precise.
Performance RenderFidelity is recommended more for geometrically dense smaller objects that don’t require detail to be shown (ex. foliage). Automatic, like the name implies, will let Roblox calculate the fidelity detail.