Anyone know how to capture NDSP plugins with the quad?
There’s not really anything special you need to do. Turn off compressors and any other time effects (delay, reverb etc)
Read the QC manual, and follow the onscreen instructions. It’s pretty straight forward.
there is such a warning that people are afraid to do anything with the capture, by the way, I am among them 
What issues are you having?
probably a general misunderstanding, I will assume for the author.
INST to RET1, OUT to monitors, CAPTURE OUT to sound card input, PLUG-IN, sound card output to input IN 1 ?
also, instead of a plugin, there can be any effects pedal?