May not be the camera/camcorder... but the monitor on which you are watching the playback - at 4k. Use your favorite browser and search engine and search "judder". The 4k issue has been known for a while. You can either set the monitor "motion control" or don't record using 24 fps... Use 30 or 60 FPS instead when recording.
24 fps is overrated. In the day that was the selected frame rate, 24 frames per second was designed for film capture. It is the slowest capture frame rate where motion still looks "natural". Remember, when film was "the way", film was very expensive and cost even more to edit. Use less film at 24 fps = spend less $. And in order to edit, the film had to be processed. And multiple takes were really expensive...
Today's digital implementations don't need to save $ on film or processing. There is no film involved.
For this issue, ISO will have little impact unless your lighting is poor - in which case, improve the lighting when the video is captured and get it to where you want in post production.