APFS - Have I reinstalled MacOS correctly?
You have a useless APFS container with a size of 2.4 GB (disk0s2/disk1) and a second APFS container with a size of 248.3 GB (disk0s3/disk2) with the default set of APFS volumes.

A default install of macOS High Sierra on your internal SSD is expected to look like this:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *251.0 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                 Apple_APFS Container disk1         250.7 GB   disk0s2        
/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +250.7 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume MACOS                   15.1 GB    disk1s1
   2:                APFS Volume Preboot                 22.8 MB    disk1s2
   3:                APFS Volume Recovery                506.6 MB   disk1s3
   4:                APFS Volume VM                      3.2 GB     disk1s4




Booted to Internet Recovery Mode or a second boot drive I would completely erase disk0 to one APFS container and either reinstall macOS High Sierra and migrate personal data with the Migration Assistant or restore a current Time Machine backup.