@emullis said:

I'd like the audience to just see the streaming data of, say, the x coordinate of the left elbow

If you right-click the Rokoko Studio Live Watcher and select the top option from the contextual menu ("Show Actor Help in Browser") there's a list of joint names. Rokoko doesn't have a tracker on the elbow, so you need to pick 'left-upper-arm', 'left-lower-arm', or do some math yourself to figure out the likely position of the elbow.

These joint names can be put into the 'point sel' input of the Skeleton Decoder actor to make it show data for just that joint (or just the selected joints if you provide a list).

I've used IOS Screen Mirroring to a Mac. There's an app called True Visage that hides all the phone's camera settings, just sends what the camera sees, which is handy.