So it turns out the family laptop has a high refresh rate (like 120 or 165 Hz) display on it. Which means that ngscopeclient can update that fast too (the waveform refresh loop is currently locked to vsync in an annoying way that prevents it from running faster than the monitor). Just ran a quick test with a ThunderScope and 5070 mobile: 10M points per waveform, FFT + waterfall at 100 Hz refresh rate. Not bad.