As for the band including myself on the piano we are all using our own Rolls PMS351 (Personal Monitor Station) that we then connect to the Rolls PS16 that supplies the DC power to our individual PM351s. the Rolls PM16 is then connected to the snake (XLR in) which sends signal from FOH to our PM351s. The tech engineer then feeds us all even signal of every instrument and vocals. The PM351 gives us the ability to turn up our instrument volume without effecting band or monitors of the church. So, as for that set up we are all very happy. IDK how the guitarist managed to do the same but using his PODHD500X and he does use IEMs which he also enjoys very much since he was also able to have a stereo setup in his IEM controling botht the over all mix and his guitar volume without effecting band members.
As you mentioned the Helix is a signal processor and NOT a mixer but I am trying to find a way to do the same as the lead guitarist because we do NOT have monitors in front of us and we all rely on IEMs. I will try those ideas you shared and I appreciate it!