I've seen some suggestions about not allowing free disk space to go critically low or
... to have no less than about 15% of your drive's capacity free ...
Currently, I've been silencing the "disk full" notification for a day now, but haven't observed any performance degradation.
"The risks involved with low disk space" is the theme of the question. More specific questions are:
What processes will see a problem in low storage space (except spotlight, assuming I don't use it.)?
Is there an official backing for the claim?
MacBook Air 2017, Mojave.