OK, CV it is then. The sequence for AT 2019xim must have been added after I took the data, which is not surprising. My observations were completed within 48 hours of the ATEL being released.
My SOP for all variables except the very brightest is to take 30-second subs and stack in real time. That way I can estimate the SNR and move to another object when it is high enough or very obviously too faint to be measured with sufficient precision. Stars which can vary by several magnitudes between successive observations can easily turn out to be saturated or invisible if purely dead reckoning is used to set exposure lengths.