If your asset is already low poly there's necessarily no need to create LODs, sub 1k vertices for example, or a small props that get culled away early anyway. These days creating LODs can be pretty much completely automated and the UE auto-LOD generally does a good job creating LODs for your props. For more specific cases…
Assuming you're not given onscreen tri-counts to hit then you should aim to LOD when triangles get smaller than a pixel - it's at this point that things become extremely inefficient. Because I'm old and I've worked mostly on very detailed console FPS games I become uncomfortable when people chuck just stuff through…