Double Concurrent Restore from one backup for 3 node AG?
All things being equal is doing a double concurrent restore from one backup to two instances an optimal timing choice?


It is definitely faster, since the wizard is doing it in sequential order. 

You can use sqlcmd or powershell runspace or (possibly coming in dbatools cmdlets) to do parallel restores. 

To even speed up that, split the full backup into stripes and enable instant file initialization.

note: make sure that there is no adhoc log backup happening since it can break your lsn and your restore.