Hi InformaticaCT,

A CGAX-7856M6 does not support more than 6 screens. When you place another CGAX-7856M6 you could connect another 6 screens. No need for Crossfire just let them run independent.
Yes there is a good chance that with the active adapters your configuration will be recognized at boot. Also you can make a Preset in the Crimson software, in case the system for whatever reason does not recognize the configuration, you can just load that preset setting you saved.