UI haven't used RED in a year or so, but the principle is the same as far as I know. Red Cine will show you the "interpretation" of your footage, the way your DP set the aperture, ISO, gain and so on. In AE, using the settings you mentioned, you see the RAW file without any interpretation. All the data is there and you can Color Correct the footage as you see fit.
If you are happy with what you get from Red Cine, then export your footage from there in a format that AE can work with.
The thing is, by having the "preserve RGB" checkbox checked, am i still working over the raw data? It's the only way tha footage looks exactly the same like in red cine.
And thanks for the link, that video actually showed me the real power of working over the raw footage, however i found the "more options" window to be a little limited, because it works like an outside application of AE, i mean, i can't for example do a mask in certain part of the shot and work the color temperature only there, do you know what i mean?
The way I did color grading on RED footage was to take the raw look ( no preserve RGB) and start from scratch. I used multiple instances of Colorista and/or some of the basic Color Correction plugins (Levels, Hue Stauration...) together with masks (either on duplicate layers or on Adjustment layers). I never used preserve RGB, and I'm not sure if or how it limits the color depth.