Here is another basic composition and 3D render test: I am reusing CamTrackAR scene that I shot and tracked on the iPhone the other day. The jitter does exist, but hopefully something that the app can fix in the future.

I use my own body scan and applying a dancing mocap animation from Mixamo and place it in the scene. I am using liquid refraction shader. I render it using Cycles. With Eevee possible but Cycles gives more realistic refraction.

The shadow is still slightly wrong and I might need to try using 3D projection mapping to make a dummy scene.