I’d just like to add: That particular MIDI pedal also features LFOs, transmitting MIDI CC. If you end up exploring that route, it’s possible to overload the H9 MIDI Input (lots of continuous data). Especially if you’re controlling multiple H9 parameters at once, transmitting multiple CCs, or using very rapid rates.
The Reflex will transmit other MIDI messages: Aftertouch (unsupported in the H9), and Pitch Bend. The latter is ‘double-precision’ (like the CCs). It can be useful for smooth pitch shifts and it’s ‘return-to-center’ capability (not as useful with the MIDI expression pedal). I find that easier to nail with a ‘tighter’ treadle adjustment.