Hi, I would like to know if it's possible to create multiple member categories and to have email confirmation when a user registers. Also, is it possible to add some coding to embed some plugin. Thank you! Marc 

Yes, with the UltimateWB members/social networking built-in app you can create multiple member groups and also customize a user registration email to get sent to the user.  Please check out the User Manual Social Networking apps section at https://www.ultimatewb.com/members-social-networking-app .

Yes, you can add your own coding/plugins using the Ad(d)s Manager in your website admin panel: https://www.ultimatewb.com/adds-app .