Ionic 6 application - can I use signInWithCredentials?

I only started looking at Okta yesterday so I am extremely new to all things Okta. We have an Ionic 6 / Capacitor / Angular application which has been in production now for a few years and we need to add Okta authentication.

I have added the OktaDev Schematics library to the app (which automatically adds the Ionic AppAuth library). I am getting somewhere - I can re-direct to the Oka Login page from my app and on logging in I get re-directed back with a token.

My first question (I say first because I am guessing I may have more over the coming days) is how I might be able to pass a user’s email address to the sign in call so that on the Okta login page the user only needs to enter their password and not their email address too? (reason being that in our app we have to have the user enter their email address first so that the app can determine whether or not this user has been migrated to Okta authentication or whether they need to use our existing method)

The authService that is added as part of the Schematics library does not seem to have any option for passing credentials across (unless I am just not seeing it). However I noticed that the okta-auth-js library does seem to.

Should I be using the okta-auth-js library in addition to the two libraries I have already installed - I don’t want to overcomplicate things too much if possible. Any advice would be appreciated?