Below are some of my guesses and assumptions:
When sending a 1MHz signal into the SDS2000X HD, it looks like each trigger cluster has a period of about 16.28ms, suggesting that the screen update rate could be around 61FPS.
Trig_Out-1: 1 cluster = 31 - 14.72 = 16.28 (mS)
1 / 16.28ms = 61.43 FPS
I know most of us usually think in terms of 60 FPS, but these numbers are just derived from my observations.
In another test, 1MHz bursts were sent to see if the trigger signal keeps its tempo. It seems to do so, as the timing is likely to be an integer multiple of 16.28ms. This suggests that the screen might be updating its screen at 61Hz, independent of the signal timing. There's another story for slow signals or processing bottlenecks.
Of course, to accurately observe the real delay between the signal and the screen display, a high-speed camera would be needed.
Trig_Out-2: (112.6 - 14.72) / 16.28 = 6.01 ≈ 6
Trig_Out-3: (373.8 - 14.72) / 16.28 = 22.06 ≈ 22
Trig_Out-4: (863.5 - 14.72) / 16.28 = 52.14 ≈ 52
In a previous rough test, the SDS2000X Plus was estimated to have a screen update rate of about 30 FPS.