Oauth 2 authentication server in ASP.NET Web API

Question

The company I work with develops internal applications, but for policy reasons, we will have a subdomain to handle authentications such as: login.dominio.com.br where you will have an app responsible for administering customer data in a separate database from other apps.

That way I’m studying more deeply Oauth, to better understand how it works. I did some local tests and from what I understood in simple mode the code snippet below that is located in the Startup.Cs class configures the authorization server:

 OAuthAuthorizationServerOptions OAuthServerOptions = new OAuthAuthorizationServerOptions()
        {
            AllowInsecureHttp = true,
            TokenEndpointPath = new PathString("/services/authentication/oauth2/token"),
            AuthorizeEndpointPath = new PathString("/services/authentication/oauth2/token/ExternalLogin"),
            AccessTokenExpireTimeSpan = TimeSpan.FromDays(1),
            Provider = new AuthorizationServerProvider(service)
        };

        app.UseOAuthAuthorizationServer(OAuthServerOptions);

The Authorizationserverprovider.Cs class is responsible for accessing the database and making the validations.

The first question is: Do I need to use ASP.NET Identity to manage my bank? or I can use Oauth implementation documentation with Authorizationserverprovider.Cs to store manually in the bank?

The other question is, can I find a template or a full post on how to do all of this implementation in a way that meets these requirements? Because all I find on the internet is just setting up for other providers like Facebook or Google.

The question is just "Create my own authentication preview", consuming would be another step.