Hashcat AMD Driver support
Just some clarification here:

The homepage says that I need: 
  • AMD GPUs on Windows require "AMD Radeon Software Crimson Edition" (15.12 or later)
Does this mean I can only use the latest version of the "Crimson Edition", or can I interpret "later" as support for the latest driver package?

Crimson ReLive Edition, or even Adrenalin Edition? Are there specific builds of each that I should remain under? Or is it as simple as 15.12 or any version, variant, or build there-after up to the latest driver as of today?

--- Additional side question: Can I run 2 independant GPU's to do hashing? E.G 2 AMD GPU's that don't natively support Crossfire?
You can use most any build newer than 15.12. Crossfire is not needed for hashcat. You can use 2 “independent” GPUs.
Thanks, latest driver, and dual R9 GPU's seems to work.