According to this, humans can't see flicker above 100 Hz for most smooth images, but if the image has high frequency spatial edges then they can see flicker up to 500-1000 Hz. It has to do with saccades.

https://www.nature.com/articles/srep07861

Single chip DLP projectors strobe red, green, blue, white sequentially. Modern DLPs use separate light sources (LED/Laser) and pulse them at a high frequency - kilohertz I assume. Before we had high-power LEDs DLP projectors used a xenon lamp and a color wheel (https://www.projectorjunkies.com/color-wheel-dlp/) spinning at as little as 60 revolutions per second. This caused a "rainbow effect" which was very annoying to some people, but apparently enough people didn't notice it that those products got sold anyway. So somewhere around 180Hz is the bare minimum.