The point seems to be the filtering. Here's an image and capx of different events doing exactly the same thing.
1. First way is super heavy as it does not filter at all, goes through all and does it.
2. Second way is a bit cheaper as it filters by is on screen first. Very useful.
3. Even better is this weird way. On par with behaviours. First Checking opacity across the entire layout, picking the closest one setting it to 50, moving on to the next closest one setting it to 50, until it reached the distance limit of 150. Another event does the reverse thing to set it back to original opacity outside the distance limit. Super cheap and efficient.
4. Using the Line of Sight behaviour to do exactly the same thing, sligtly cheaper than no.3. Line of sight can even replace "is on screen" as an even cheaper substitute for filtering by screen size if you set the radius slightly bigger than the window width.
Conclusion, there are some good ways to do things and some bad ways. So far line of sight, and 'pick nearest/furthest' seems to be the most efficient ways to pick/filter.