Depends on what you want to store there, what your requirements in terms of features, data integrity, performance and so on are.
You will have to format them with the storage of your choice (VM/LXC Storage: ZFS, LVM, LVM-Thin, btrfs; or for file storage: Directory).
They are all consumer SSDs of different sizes, so I would probably stick with "LVM-Thin" in case you want to store virtual disks there or "Directory" if you want to store files (like ISOs, backups, templates, ...)