The main way to know if your case has been processed by the PEB is to ask your PEBLO or MSC if they show your case as "Pending DRAS". That would mean that AFPC / the PEB has unofficially decided that you're unfit and has sent your case to the VA to be rated.
Once rated, the VA will send it back to the PEB for them to draft up you DOD ratings. Once drafted, they will send your proposed DOD / VA ratings to your PEBLO so that you can briefed.
If the VA is telling you that your case is "Pending a decision" your case might not have been sent yet. I found out that my case was sent from the PEB to the VA when the VA agent told me that my claim was in the "Ready for decision phase". If you want more information, schedule a virtual phone call through VA VERA. They can give you information on if your claim has been sent to the VA or if it's been assigned to a rater.
Hope this helps!