This is basically for confirmation, but I might be wrong.
If I'm trying to get certain users to use SSO only, I don't need to have them set up a Salesforce password correct?
I'm under the impression logging in through the salesforce log in page and logging in through SSO are two things that don't touch.
From https://help.salesforce.com/articleView?id=sso_tips.htm&type=5:
When an authentication provider is enabled, Salesforce doesn’t validate a user’s password. Instead, Salesforce uses the user’s login credentials from the external service provider to establish authentication credentials.
But does a user need to have a password at all is my question.