chlorine/chloramines are harmful or deadly to your fish depnding on the concentration. Your best choice it to leave it sit overnight.
RO/DI is a must for a DT. QT's are temporary holding, and most get drained between uses. You aren't concerned about algea growth that comes with the excess dissolved solids in it. You don't need it to strip copper (really, the levels you would get even with all copper piping are low, and only build over time) and you are adding copper anyway.
For a QT, I never worry about the water source...Beyond that, I usually do my changes in the QT with water from my DT, snd replace the water in the DT with fresh mix. Those extra water changes are mostly meaningless, but since your prepping to add more bioload to it, its nice to think its "extra ready"