On multisite it’s still a single user table for all websites. It identify user relationship with sites on the table wp_usermeta, under the following user meta keys:
- wp_x_capabilities
- wp_x_user_level
There are other meta keys for user options. But I guess there is no difference on other meta fields (like name, display name and etc), so the user will have the same frontend’s meta fields for all sites on the network.