Usually you put the modulation pedals in the FX Loop so chorus, reverb, delay etc.
This is so the pedal is untouched by your preamp and sounds cleaner and more precise in what’s it meant to do to you sound(as it was designed.)
The fx loop is after the preamp but before the power amp so putting boosts in there can overdrive the amp
Also a lot of loops run at line level not instrument level so if the pedal sounds like crap it’s not designed to run at line level.