Like others said, I use the two Aux sends (post-fader) of my Mackie 1202-VLZ Pro to send all my sound sources - Eurorack, other synths/samplers, live bamboo flutes - through looper/fx pedals and a Eurorack sampler/delay. One Aux send (the FX Send on your mixer) goes out into my Eventide Timefactor --> reverb pedal --> back to the Aux return (ST Return on your mixer), and the other Aux goes into my Eurorack sampler Reflex Liveloop, and the module output goes into one of the stereo input channels so I can control the level a bit better. On that channel, the Aux 2 level is at 0 so its output doesn’t feedback onto itself.

I have the Aux levels on all channels, Aux Master and Return levels all at noon (Unity) position and haven’t experienced any clipping problems as long as I manage the individual input channel levels. And then everything goes out the main outputs of the mixer. I’ve had my setup for live performance many times and haven’t had any level problems.

For your set up, then, you’d connect all your sound sources (computer via Audio 6, TC voice pedal, Yamaha) into individual input channels. Connect the FX Send outputs to the inputs of your RC-300, and the outputs of the RC-300 to the ST Return, and you use the yellow knobs on each channel to control how much signal from each channel goes into the looper, and the ST RTN fader to control the level coming from the RC. If you’re not recording anything in Ableton and using it mainly as an instrument/drums playback, you’d just route the output of your laptop/audio interface into an input channel on the mixer into the PA. You want to make sure you’re not sending any audio back into Ableton with channel inputs and monitoring turned on in Ableton, which is where you might be getting distorted/phased sounds.

Hope this helps!