Apple could have chosen to make APFS open source or to document it fully, to help third parties develop maintenance tools. It chose not to, but Disk Utility still doesn’t work as it should.
snapshot
It depends whether you’re going to boot macOS from it, on the space required for snapshots, and how large they could become. And there’s more.
Have you found Time Machine docs helpful in solving problems? Do you know what “custom access” means in the Permissions section of Get Info?
Why Time Machine makes snapshots, and how they can grow and apparently consume free space. What you can and should do to manage this.
One likely cause of vanishing free space are large snapshots. So how can you tell why a snapshot is large, and how can you avoid it?
Snapshots are of great value, but can grow large if you don’t keep an eye on them. If you find Time Machine or another backup utility is storing large snapshots, here’s what to do.
Confused by this on APFS? So you should be, as it’s complicated by features like snapshots, sparse files, and the file system itself. There’s no single figure.
Tired of HFS+? Disenchanted by APFS? Why not copy or back up to a different file system? Here are crocodiles waiting to bite you.
How to repair a snapshot with an error when it’s one of your backups on a hard disk? Currently this seems impossible, putting all those backups at risk.
Explains the identifiers, sizes and tidemark data shown for snapshots in Disk Utility, in Monterey.
The Eclectic Light Company 