Check out my setup as it allows for a lot of flexibility. My signal flow goes like this: Guitar --> HX Effects (mono out FX Loop) --> Kemper --> stereo out back to HX Effects (stereo in FX Loop) --> stereo out to Mod Duo --> stereo out to stereo DI. From there, I do a stereo out both to the front of house board and I do a stereo through to my stereo monitor, which was the Yamaha THR10 (via the stereo input, which should be flat), but is now the Vox Adio Air. I also go to the stereo input, which should be flat, so there is no coloring.
The HD500 acts as my midi controller (I know, it totally needs to be replaced). But yeah, the new Duo will have a USB interface, so for recording purposes, you should be able to use that. But yeah, that’s my setup as I just use the mini amp (THR10 or Adio Air) as my stereo monitor. If you have a loud band, you are going to need a much more powerful amp, and possibly 2 of them if you want a stereo setup.