Boss NS2 vs EHX Silencer vs TC sentry / fx loops

my current chain is Digitech Main Squeeze > Keeley D&M Drive > EHX Flatiron Fuzz > Mooer lofi machine > Boss RV6 > orange crush 35rt amp.

I don't have any issues with hum/buzz but i'm itll start to get noiser as I add some more pedals. I mainly just want to tame the feedback/squeal when I have the gain cranked and Im not touching the strings. I have heard equally good things for all these pedals, but I'm currently leaning towards the EHX Silencer as I can find it a bit cheaper than the others.

The main question I have, as im not very experienced with pedals (i used to use a zoom g1x and modeling amp), what exactly does the send and return/fx loop do and how do I utilize it? I have found that most people say to use the fx loop with the gate and to run my drive pedals through the fx loop. My amp also has an fx loop, Is there a way I should be utilizing that? Thanks!