All Apple Photos plugins (including Photo AI) save files back as JPEG. Apple Photos does not allow a plugin to save back a RAW file. The TIF extension showing is a bug, it will be a JPEG.
Please clear the registry for Photo AI with instructions below and see if that fixes the white screen issue.
Delete registry for Topaz Labs applications
I added an issue for this so we can reproduce and fix it.
Could you try the registry deletion steps as well? Delete registry for Topaz Labs applications