Creation of new users

I am thinking about instantly migrating a user from 1 site to vanilla after registration.
I looked through the db schema and noticed in the gdn_user table there is an attribute col that is stored as json.
my question is, do i need to instanciate this col when i import the user or will this field populate upon login?
Furthermore I am going to use JSConnect plugin and I am curious about the password field. Will i need to generate a random hash for the pw or should I just leave it as is.
thoughts?
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