Warbringer
Explorer
I'd do light club 1-handed, 1d4, using the nunchaku to stoke with 1 hand, or 2d4 2handed using them in classic perceived use, switching from hand to hand
Yeah...I personally wouldn't hold any sort of nunchaku as being equivalent to a flail. The physical properties of the two weapons have some notable divergences - while admittedly there really isn't much of a consistent standard or historical record for either, the center of mass of the nunchaku is much closer to the wielder than is that of the flail and the area of impact tends to be larger; which would result in a very considerably less powerful strike. I can't find any indication that nunchaku were ever used as a battlefield weapon. They seem mostly to have found use as something cheap and easily carried that could outrange a knife.A martial nunchaku is a flail. This weapon was made for combat. A monk cannot use it in Martial Arts.
A simple numchaku is a club. This weapon was probably an improvised weapon, a lighter version of the above, or a grain or bean thresher. A monk can use it in Martial Arts.