With mouse plugged into the scrope the scroll wheel is available for making numeric field adjustments.
That's interesting, must not have implemented that in the web interface
An USB mouse only sends the displacement+buttons when polled, and the standard HID poll rate is something about 100Hz (don't recall the exact rate, it's in the HID specs). That is low enough to affect pro gamers, so there are non compliant USB ports, and non compliant USB drivers that can poll a mouse at 200Hz or more.
Another thing, LCD panels are very hard to drive at fast refresh rates, and they are usually working at less than the CRT used to. Most LCD and/or IPS panels are at 50/60Hz refresh rate, yet they do not flicker to the eye (like a 50/60Hz CRT would), because of the remanence. Flat panels are very hard to drive at more than 200Hz, and gaming monitors at >150Hz are very expensive.
My guess is the refresh rate in an oscilloscope panel would be a casual 30 or 60Hz, I don't see why I would need more than that, but I didn't measure.
The "slower" update might look so because the memory depth is higher. A waveform is redrawn on the screen at each trigger, but only after the memory is full (or at least that is how it seems to be for my Rigol DS1054Z). Because of this, at the same sampling rate, same oscilloscope will appear "slower" when the memory depth is set to higher values.
For slower ADC sampling rates, it might even take seconds to fill something like the 14 mil samples (the max memory in a DS1054Z).