Both my wife, a non-afibber, and myself, an ablated former afibber, have tried CBD in various forms; oil, suppositories, consumables,vaping, for insomnia and pain without noticing any effect so we gave it up a year or so ago. Neither of us has tolerance for THC even though we live in San Francisco much of the time.
My understanding is that CBD takes some THC, perhaps a ratio of 1/18, to enable the CBD.
It's pretty hard to find any real data on CBD - most of what's out there I've seen is anecdotal.
My current best insomnia remedies are: Melatonin, 3 mg; PharmaGaba and Theanine, 200mg, a couple of Ibuprofen or Tylenol or the occasional 5mg Ambien. My best results are when I rotate these as they seem to lose their effect if any one of them is consumed several nights in a row.
Gordon