I am happy to hear that the sandcastle demo that I provided was helpful! As you know, creating sandcastle demos takes some time so I appreciate your patience.
Off the top of my head, I can’t think of a quick and easy way to show the same results given from selecting a Billboard when selecting an uploaded model. This would be a great place for other community members to add some suggestions!
It is possible to scale the billboard! If you look over the Billboard documentation that I referenced in my last response, you will see that Billboard has the member scaleByDistance, which allows you to set the scaling properties of a Billboard based on its distance from the Camera. Here is an example of how to use scaleByDistance:
// Example 1.
// Set a billboard's scaleByDistance to scale by 1.5 when the
// camera is 1500 meters from the billboard and disappear as
// the camera distance approaches 8.0e6 meters.
b.scaleByDistance = new Cesium.NearFarScalar(1.5e2, 1.5, 8.0e6, 0.0);
It seems like your questions about 3D Tiles are posted in two different threads. I answered your questions in the other thread, which I will add here for continuity.
Let me know if you have any other questions or concerns!
Best,
Sam