I have owned the K&F Concept Dual for more than 4 months now and would like to briefly share my experience.
First of all, I am still convinced of the dashcam! Overall, it delivers a good image, even very good images during the day, although it must of course be said that this model also does not have autofocus and therefore does not focus infinitely. Unfortunately, you can no longer read license plates or signs at night, but almost all dash cams in this price range have this problem. If an accident occurs, the video can also be used to reconstruct the accident at night.
I only use the front camera. It's a shame that you can use both cameras at the same time, but only in Full HD mode. For example, if you want to operate the front camera at 60 FPS, you inevitably have to leave the rear camera switched off. The processor is probably unable to process the data. If you set a resolution higher than Full HD, I personally don't see any advantage in the image.

The motion mode works very well. I've had to brake hard several times and the camera reliably saved the current video. If you want, you can save the video yourself at the touch of a button.