Where are all those purgeable files? Two updated utilities to help you find them: Precize and Sparsity, which will crawl folders checking which files are purgeable, sparse or clones.
purge
Performed by CacheDelete, it first looks at a wide range of macOS caches, and only at the end purges snapshots, to free up space when it runs short.
Although my Mac has 6 GB of memory, I have had to use the purge command with depressing frequency since OS X 10.6, before quitting anything, particularly Safari.
The Eclectic Light Company 