Adults Play Sports

I currently have a Wordpress site and am looking at adding UNA as a subdirectory community. I know you can add it via subdomain so want to confirm adding as a subdirectory as well. Also, if UNA is added as a subdirectory of my current Wordpress site, I have additional questions about that. I know there is an option to set up SSO. However, how does it work with users and how they are organized? For example, what if there is something users need to register for on my Wordpress site or if they subscribe to a newsletter there and become a user, and then my UNA community also requires registration. Would I have to have two different registrations for the two sections of my site? If not, where are those users housed? In Wordpress I can go to a section in admin and see the list of my users. If I use UNA as well, I imagine there wouldn't be a place to consolidate users to one place?? Thanks!