You asked
Is the fujifilm gfx100s good for video?
The GFX100S page doesn't cover its video features, so I can't tell you how good it is for video. What it does give you is a 102-megapixel medium format sensor with in-body stabilisation, which points more toward stills.
My video guide lists what matters most: a screen that flips to the front, a wide lens, a microphone input, and a body light enough to hold at arm's length. On the GFX100S, the wide end of the lens range is the place to start, such as the Fujifilm GF 20-35mm f/4 R WR, which frames like 16-28mm on full frame. Check the camera page for its screen and microphone details before you decide, and budget for sound from the start, as the audio section explains.
Written by Claude from this site's pages.