What is the most friendly file format for Colorgrading Original or Optimised

Hello there,

I am wondering what would be the best format for colograding i.e using MagicBullet FCP X plugin.

I can edit H.264 from my MacBook Pro without transcoding it , but when it comes to colograding, I am not sure if I should do the transcoding and making a much larger 422 file or stay with H.264? I haven't done test yet, but would a Proess 422 made the job lot easier in terms of the rendering speed or the usage of CPU power. Furthermore, If I transcode the footage to 422, and colorgrad it in Magicbullet, would it give the same look on my monitor compared with to use H264 file, or to make the question clearer , lets make a extreme example by compare to use proxy file for colorgrading and to use H.264 file for colorgrading, and I am assuming that the H.264 file will give a lot accurate look on MONITOR than Proxy file, but Proxy file renders lots faster than H.264 while grading, is this right?

If it is correct, is there a way that I can firstly edit the entire film by just using the original H.264 file and then, I transcode the footage that only on timeline to 422 for colorgrading to speed up the rendering speed ? Well then, here comes another question, lets say If I use Resolve for grading, and I am editing the timeline on just H264 file, the way to send it to Resolve is to save the project as XML file and then open it in Resolve right, but as I know Resolve can only read Proress right? or at least Proress performs better in Resolve,. I am sorry I am so confused about all this, and I'm sorry that I have asked a rather very unclear question,,,