This option is only available if the form login feature is disabled.

Here's a quick description of how these options work when configured in each way:

Users are only allowed to create new records, but can't edit/access existing records.

Allow users to edit records without the ability to create new ones.

This will prevent users from being able to load the form so that nobody can use it. It's an alternative option instead of deleting the form completely.

If you disable Creating Records, you won't be able to open the form's main URL to create records. E.g.

You would only be able to access the URL when it has a record ID appended. E.g.

You can generate these URLs by using the formula available in the form settings. It produces a different URL for every record in your table.

If you would like your users to look up records, you would need to enable the login screen option. Regardless of its name, that option would allow your users to search for records and edit them.