If you use the node that Miguel mentioned, you can adjust the Lumen contribution on a per material basis. Just set the value for “Lumen emissive lighting contrubution” to a lower amount than the Emissive (surface appearance) value. For example, setting it to 1 means it will be 10x weaker in the Lumen contribution. Setting it to 0 will make it so the emissive doesn’t contribute to Lumen at all.