I think that the amp model or guitar you use can definitely play a roll in which OD/distortion sounds best. For instance, the Interstate Zed amp or AC30 with the Minotaur will produce a very bright, sparkly sound. They don't need a ton of gain to sound good. Even with my Ibanez RG, I get a very transparent, natural guitar sound that really brings out the different pickup positions. But it is very unforgiving and any mistakes the player makes will be bright and clear!
The Screamer is more forgiving in my opinion. The overall tone is a bit darker and smoother sounding. This pedal pretty much sounds good over any amp model on Helix. It will take any of the Marshall or other high-gain amp models into the stratosphere in terms of gain, sustain, volume, etc. This pedal also enhances and warms up the tone of any other distortion pedal that it is paired with. Such as the Minotaur or Rat.
The Rat alone with add some aggressive crunch to heavy sounds. But In my opinion, the amp needs to be set to sound pretty chunky with a smooth sustain to keep everything from sounding too harsh. Never overlook the importance of trying LESS presence and MORE midrange as a possible adjustment. Adjusting the characteristics of the tubes can sometimes help as well.
Another very important feature to remember is which mic is set in the amp settings. Ribbon mics sound totally different that dynamic mics, etc. And as always, your tone will only be as good as the monitors you're hearing it through.
I'm pretty happy with everything I've used with Helix so far. It does take some trial and error, and updates often help improve tone. I hope my two cents can help you out in some way. Good luck and have fun with it!