I am considering getting the 27" 5K iMac but not sure which GPU to get. I've been looking at the baseline model with the R9 M380 but not sure if this GPU is good enough for my uses. My primary uses are Photos, very light iMovie video editing, iTunes, Safari with about 12 or so tabs, and (rarely) occasional gaming. (Nothing hardcore like Witcher 3 or FPS games, just random stuff like The Long Dark or Ark. I have no illusions about playing smoothly at native resolution and wouldn't mind dialing down the resolution if the frame rate is decent.) Actually, since I rarely game, if we take that gaming piece out of the equation, is the R9 M380 sufficient for my uses? I don't want any stuttering in the UI or anything like that. Also, how much RAM is recommended for light video editing in iMovie?