Helix allows you to add Global EQ to 1/4", XLR or both outputs. When building presets, forget that Global EQ exists. Make it sound good coming out of mixing monitors.
An intended way to use your modeller is to send XLR L/R to FOH, and use 1/4" for stage volume, to be able to hear yourself. Or use in-ears. In order to hear themselves on stage, many people use an FRFR, a power amp + cab, or go into an effects loop of an amp + cab. In all 3 cases (with some exceptions), there is no way to adjust your EQ.
So.
If you go direct to FOH, then:
Global EQ is meant to be able to adjust your on-stage sound and nothing else. Sometimes you go to play a show and the stage is super-resonant, and it keeps rattling when you play a certain note or chord. Or the stage is surrounded by ceramic tile, and your ears are hurting because everything is loud and shrill. Global EQ to the rescue! Unlike your typical amp high/mid/low, Global EQ is extremely flexible.
When I toured, I mostly left the Global EQ off for the on-stage amp. However, since the clubs I played were not all huge, sometimes the on-stage sound would interfere with the overall mix. That's when the sound guy would ask me to adjust my sound a certain way. Or sometimes, the stage is too boomy, and I would have to make the adjustment myself so I would not sound like one of those cars with a giant subwoofer in the trunk!
In summary:
Leave the direct FOH mix to the sound guy. Don't add any Global EQ to the XLR outs. Sound guys can apply whatever EQ they want to what you are sending them. Use Global EQ to compensate for the unforeseen stage acoustics. And nothing else.
Every room is different. Even if you play with the same exact lineup, same exact club, same exact sound guy several days in a row, the room may sound different on any day due to: humidity, temperature, number of people, where people are, how worn out your strings are.