What you are asking is not related to the HMD itself but depends wholly on the computer you are using to power it.
The 5k+ with the latest firmware goes up to 120hz as long as your computer can deliver that, regular monitors do 60hz, gaming monitors usually 120hz or 144hz, enthusiast grade goes to somewhere around 240hz i think.
DSR is extra resolution so thats extra strain for your computer, might lead to extra lag.
Motion smoothing id guess decreases the framerate with the intention of giving a more even flow of frames but will likely induce some input delay.