One meter is fine 95 percent of that time except when you need that one extra foot that you can’t get every once in awhile. So I would say 6ft/2m is ideal. The two limiting factors have come across in these - one is the stiffness of the cable. None of them are that stiff and you end up having the end flopping and twisting around which makes it even more challenging. The other is the size of the head and cable. The smaller the better. I had to snake a camera between a pocket door and the slightly thicker unit couldn’t make it in.

you should also consider the ones with a 90 degree side camera on then. With a push of button can see the side which has come in handy more times than I can count.