Getting username in SWA app

I need advice on two things. My use case is that , I am a software vendor writing an integration for a client using OKTA. I want my app to be in the client’s OKTA org, user clicks on it & SSO’s into my app outside OKTA.

Question1: Is SWA the right Integration? If so, then

Question 2:
I wrote a SWA plugin in OKTA. I am able to authenticate and redirect to my specified redirect URL. But how do i read the user name from this redirect? The request body of the redirect from OKTA is empty.

Please help or point me to SWA sample/documentation.

Thanks for the help.