Another thing on SSDs that I was thinking about: Would TRIM work/be functional on an encrypted disk? I presumed that free space on a disk is also encrypted (and thus never be marked as available space on the low level that TRIM will zero), but it turns out File Vault (File Vault 2 whole disk encryption) doesn’t work that way. The free space is not part of the vault, and TRIM will empty those blocks just as with an unencrypted disk. Encryption purists wouldn’t be happy about that, as even the amount of free space could be a marker, that real full disk encryption wouldn’t give away.
I'm pretty sure that joemike has posted that full disk encryption in APFS High Sierra encrypts even free space.
