As I understand it, all three will be able to operate simultaneously?
The alternation schemes in the R3 proposals show, at any given point in time, one runway dedicated to departures, one to arrivals and one of the two outer runways operating in mixed-mode (interleaved takeoffs and landings).
So different (more) air space is being used.
In the absence of any published flightpaths, it's reasonable to assume that most, if not all, landing traffic would follow conventional straight-in approaches from a minimum of 8-10 nm and departing aircraft would join the existing SID/NPRs. Curved and/or steeper approaches will no doubt come in time (with or without R3).