Hi @KelvinShah ,
So Okta is a identity provider and in order to implement SSO, I guess you you must be using SAML or Authentication Handler. In web console Adobe Granite SAML 2.0 Authentication Handler you can manage several configuration related to SAML.
Here you can also configure that after successful authentication whether or not to automatically create non-existing users in the repository. So, I believe existing user will remain as it is, but for safer side you can try to simulate the behavior on any lower environment before moving to higher env.
Hope this help!