OKTA for Angular SPA UI with Spring boot API

I am trying to implement OKATA SSO authentication for my application with below details. can you suggest the right pattern to be used.
UI - Angular SPA
API - Spring Boot (Rest API backend)
For UI, I am using Authorization code flow with PKCE. But I am not sure which pattern to use for backend API service.

SO far I have created only one client app in OKTA for authenticating my UI app alone.

which approach would work.

  1. Just pass the ID token to API service and validate Or
  2. Create separate client app for API service and follow authorization code flow for API.

Please suggest the right patterns. Thank you for your help.

We have two Angular sample applications, one uses the Okta hosted login, and the other a self hosted Widget.

Both Applications are setup to use a backend resource server (protected API). We have a Spring sample application of the resource server that can be used with the sample Angular frontend app.