The use of REDCINEX is strictly for first light color editing.
I dont have enough experience to claim that it can be used as a final grade option.
As far as scaling, you have to find out what your target is.
With all this scaling talk I fear that your moving all resources to the base clips settings which sounds like 5K.
Now thats a freakish high number and I own an Scarlet and I rarely use 4K as my final settings.
Well I do when I feel like testing YouTubes 4K options 🙂
If your final output is 2K then use that setting but thats only if your stuggling with mixed media e.g. NTSC, HD and what ever flavour 2K/3K/4K/5K/6K? your using.
Also, if you are planning to export to 5K (why?), I believe you have to change your ProRes 422 to ProRes4444.
Sorry If Im not specific with my input.