Putting a looper in the FX loop can be a good thing or it can be somewhat limiting – what you put in the loop is what you get. I never know how much gain and exactly what tone I want going in with a particular loop. I like to lay down a clean loop in the looper and then add an amp sim/preamp type of pedal after it. In my case that’s usually the Joyo American Sound. Drive pedals in the FX loop can be cool too. That way I can add gain, and other tone/EQ changes to the loop on the fly. Putting an amp sim pedal in the FX loop will also color the overall tone. It’s another tone layer that I’ve come to like.
Plugging direct into the FX loop return opens up cool options as well. The American Sound shines in this scenario.
Mucking around with pedals in the the FX loop can open up some cool “Greenfield” tone tweaking:
That said, my next move could just as well be a microphone upgrade and/or an external speaker cab.
Don’t sleep on how cool an FX loop can be.