Found this from the manufacturer: "When the refresh rate is higher than 60Hz and can be detected, the screen resolution will be reduced to improve the refresh rate" So it seems like anything above 60Hz will be 1080p rather than 4K.
The Fengmi V10 4K Projector is now available globally via Banggood. The gadget has a 240 Hz refresh rate and 12 ms latency, which the company suggests gears the device towards gamers. The device can throw images up to 180-in across and supports HDR10+. You can cast to the projector via Apple AirPlay or connect through HDMI ARC and 2.1 ports.