I’ve got the Smoothskin Pure and I used it pretty much all over down there
it’s a stubborn area and I wasn’t always consistent enough with it but I have absolutely no hairs on the outside of my underwear area now and the triangle bit grows back really slowly and is a lot softer and finer. Further down it maybe grows back a bit slower and not as coarse but it’s not much of a difference. However if you were consistent you might get results. I always used mine on its lowest setting.
I will add that years ago I always used to get it all waxed off and if I ever shaved it would be so itchy and horrible. It’s not like that anymore so even the little I’ve done has made a difference.