What happens after WHMCS install

How is the integration differ from simply using the WHMCS installation in a subdomain?

More specifically...

Currently I have WHMCS on a subdomain.

After installing this plugin in WordPress it doesn't actually add anything to the admin area. Is that correct?

For example, at the moment, my clients can do their client stuff through the subdomain. What benefit does using the integration plugin offer?

Would I have to setup those WHMCS pages on some WordPress pages on a particular site in the network where clients could then login to check their account details?

Excuse me if this is a weird question. I'm just trying to get my head around the use case scenario for this plugin.

Cheerio and thanks,
Peter