I mainly set the draw distance on the light - to what distance should it be drawn.
light radius - the smaller the better. In advanced settings, there is a light falloff exponent, in case you want the light to shine near the border of the radius.
If you can shine a light without a shadow - it is very cheap.
I don’t use pointlights, only in rare cases - they are much more expensive in terms of performance than spotlights. Spotlight with large radius can be preaty heavy. same for rect lights.
I don’t rely on Lumen, its indirect lightning and emissive materials - they are turned off on medium settings, but they increase your FPS performance a lot (in my case, even double). that’s why I have set the scene so that it looks very similar both on Epic and on medium (it is necessary to match DFAO for medium details (skylight settings) and skylight leaking (postprocess volume settings for Lumen).
But for medium settings, i needed turn of DFAO specular occlusion on 5.3.2, because it doesnt work properly (interiors were grey and shiny as hell)
I don’t use distance field shadows anymore - they are still turned off on medium.
I pay attention to the light in the interiors, so that the light complexity does not increase - a pair of lights, half on one side of the wall, the other on the other can cross radius and can cause more fps drops.
Less is better - sometimes is better less lights for better atmosphere (like 70 percent on screen are shadows).
For classic shadows, there is max shadows distance and distance field shadows distance options