I have talked with people with RLS and they indicated it did help, and they were advocating for our state med cannabis program to add it.
I talked even more extensively with persons with Phantom Limb Syndrome which is very similar and they said cannabis was the ONLY thing that worked for them and it was a life saver.
There was a small study recently on RLS and cannabis but the numbers were small, like 6 people, but most (5?) reported complete success and the 6th found success with CBD.
Cannabis is known to help other movement disorders like Parkinson's and also be of great help for side effects of RLS, like sleep problems. Likewise,cannabis and all things "pain" is a match made in heaven
Cannabis helps tune up the nervous system/messaging transmission/reception so there is every reason to believe it should help RLS.
Which strains worked? Most seemed to find best results with Indica dom strains but with THC in there too. Yet, some found heavy THC hybrids work better.
And probably experiment to find a daytime strain and a nighttime sleep/knockout strain