Thanks for your helpful advice!
We are certainly going to be using xenforo.
Yes Oauth2 is supported by auth0 and we actually have all the things needed for that in or dashboard. I will take a look at the existing Intergrations and go from there. Can't wait for xenforo 2 to see how this all pays...
I am the technical lead for a brand named DailyDrop.
I am interested in using xenforo as the community software of choice for our startup.
I am currently running a Auth0 authentication backend (https://auth0.com/) which will eventually be used to authenticate every one of our apps.