Correct, there is a postview setting, and when I disable it, every time I take a shot with the app, it then spends 10 seconds “processing” the image before I can take another shot.
The button on the camera still lets me take 2-3 images per second. It’s unfortunate that I can’t use the app to trigger the shutter as quickly. It looks like the only option is the “Ricoh Theta S String Remote Trigger”.