The Bulk Import Method involves exporting your data from your current password manager and importing it into Passwords, whereas The Online Method involves moving credentials over one-at-a-time by signing in to their associated accounts, cleaning up your collection in the process. Although it’s possible to import your passwords into Apple Passwords from Safari or the Passwords pane in System Settings prior to macOS Sequoia, I strongly recommend doing it from the Passwords app on macOS Sequoia, because its importer is more robust than the one in older versions of macOS.