This question was never asked on the DPreview Fuji X forum, as far as I can tell.
Reviews of the Fuji XF 18-120/4 PZ say it's intended for video, and excellent for that purpose. But it's heavy and expensive.
So I was thinking, the XC 15-45/3.5-4.5 is also PZ (power zoom) although not nearly so parfocal. I like to zoom in and out during video. Would this lens be a better alternative for that than the XF 18-55/2.8-4?
Several YouTube videos answered this question.
The PowerZoom is slow and smooth, so I'm sure it would be better for video than manual zoom with 18-55/2.8-4. Cameras in the YouTube videos were able to retain focus during zoom, although I don't believe the 15-45 is parfocal, or not as close to parfocal as the 18-120/4 anyway.
Reviews complain about hum from the power zoom, a concern if you are recording live sound. Haven't seen this complain about 18-120/4.
For still photography, owners complain about sloppy feel of the front zoom ring, also used for focus in manual mode (rear ring is power zoom).
So I think I'll order X-S20 with 15-45 rather than 18-55. I probably wouldn't use the aperture ring anyway.