I haven’t bought an expression pedal or an aux switch just yet.  I’m interested in the Reflex from Source Audio and a 3 button switch.  I am a big fan of sculpt and the room reverbs on the space settings.  The Pitchfactor ones are great, but you need to adjust them as most of the presets are too extreme.  The synthonizer and octaver are getting some love from me at the moment.  Its still really early doors for me.  I have a LOT of work to do before I am comfortable with it.  

The first expression pedal I bought was from Source Audio (not the Reflex) and it did not work very well with my TimeFactor (values kept “adjusting” when my foot was not touching the pedal). With that said, it appears they do not make that particular expression pedal anymore, and they just came out with this: https://www.sourceaudiostore.net/product/soleman-midi-foot-controller .  As for 3 button Aux. Switches, the Digitech FS3X works really well because its simple. Strymon makes a “classy” 3 button Aux. Switch but it costs $100 rather than $40 for the Digitech.