There's a mod called torchmaster that lets you place one huge torch that blocks monster spawns for a wider radius. It would be awesome to have an implementation to see its effective radius on overlay.
See here: https://www.curseforge.com/minecraft/mc-mods/torchmaster

idea a) remove X where the torchmaster torch is working
idea b) color X in... green? blue? where the torchmaster torch is working