The way to "pseudo" see what is noisier than what without looking at them on the test bench, is to disconnect the preamps and put shorting input plugs on the power amp inputs, this is a better layman’s way of saying what noisier than what.
BTW some not all Class-D’s modules, don’t even switch their main section on, if there’s no signal present, they may appear to be on. And then there’s different amp gains to consider as well, as this also has a bearing on noise levels.
Cheers George