Priority Configuration iMac Pro for High Res Video Editing?

I am buying my partner a new iMac Pro for Christmas and need some help with the optimal prioritization of features for maximal benefit for least cost (within the Mac framework). She is a professional filmmaker and shoots on a RED Dragon in 6K and so needs a lot of processing power for editing. Looking at this machine compared to previous Mac options, it looks like even the base scenario could be used for this purpose, but, my question is, where would you put your money to maximize video rendering function. GPU? 10 or 18 core processor? 16 vs 8 gigs RAM? Other?

Thank you!