The answer to my question is yes, the Headrush Expression Pedal works with the Helix.
My Helix Floor came in the other day and I’ve been playing through that almost exclusively. I did some A/B’ing between the Helix and Headrush and found I can get the tones coming out of the Helix to match the tones I want to hear. The Headrush isn’t a bad product. Helix is just better. Love the amp and effect choices on the Helix, as well as the tones. My only concern is the limitation on the # of IR the Helix can store. I have a much larger # on my Headrush. I’ll handle this by going through my IR collection and putting only the ones I’ll actively use onto the Helix. It’s not a but deal, just takes some time and planning. When I make a preset that uses an IR I’ll have to spend some time swapping the IRs around to test them.
Back to the Headrush expression pedal. I connect it to EXPR2 on the Helix with a TRS cable and setup a few different patches to use it for Volume, keeping the built in Helix expression pedal for wah. The Headrush expression pedal worked fine for this. I don’t use a volume pedal often and only have a couple songs I use wah and a volume pedal at the same time.