SAML, IdP and B2B Features

Hi there,
I’m trying to understand how to allow our client to login with our application using Okta.

They have Azure AD on their environment and searching for information on Okta documentation it seems, if I’ve correctly understand, that there are multiple ways to integrate it with differents user experience.

  1. The user can use the “Sign-in with Microsoft” button we already have, that will redirect on their ADFS for the login and then redirect on our application.
  2. We can add a SAML Idp connected to their Azure AD as explained here: Make Azure Active Directory an identity provider
  3. Use the Okta B2B features but I haven’t found information about that except the (substantial) cost

Can someone explains pros, cons and differences about this three scenario? Is there any documentation that I’ve missed?