The 4 cm. The noisegate needs to detect your signal straight from your pickups because that’s where it’s most dynamic and the transients are.
so That’s the signal to activate the gate. The actual gate needs to open and close in the loop because that will kill all the hiss.
personally, I try not to use a loop at all so I’ll just put it first in line after the guitar and be okay with the hiss.
also, a pedal like the horizons devices precision drive is great because they have a built in gate that kills its own hiss, if that makes sense. Works great in conjunction with/after another noise gate Awesome pedal.