Do you want the freedom to reframe while accessing the higher than HD deliverable since you are shooting 4K?
What kind of grading process is this going to go through? Grading is more than the applying of a LUT as you have to balance shots between each other, etc. The easiest B&W method is to remove all saturation. This can be done with a LUT or using ASC CDL as I describe in my blog: https://24p.com/wordpress/?p=43
In this scenario, I would AMA link to the R3D files directly and you will be able to tell what the frame rate is for each clip in the bin with one or two of the column headings displayed (not in front of a system right now). The fps is displayed along with format, etc.
With RED, you can certainly apply a LUT in addition to using the RAW color parameters and changing the RMD to reflect the image you want to work with. Then when linking in Media Composer, apply the RMD on all the source clips. From there you can transcode when needed. Since you are in 8.3.x you should be able to transcode to DNxHR maintaining the higher 4K image to be able to reframe as needed in your 1080 project using FrameFlex.
Once complete, you can transcode final sequence to DNxHD 175x and deliver same as source to an encoder that will make your final streaming deliverables.
In this scenario, audio is going along for the ride on input – output will be whatever tracks your create for the soundtrack and what the deliverabale requires.
Michael