I honestly can’t say what the majority of shifter pilots are using. The overly-simplistic way to think of the difference between 30 and 32mm frames, apart from what I already said, is that a 32mm frame can offer more rear grip. In higher BP applications, yes, a 32mm frame could very well work better for you. I’m not talking about lateral grip at the apex, for, if the TAG kart and the shifter are on the same tire compound, that lateral grip is effectively the same. Where the additional grip comes into play is accelerating out of the turn.
But, as stated earlier, there are a lot of other factors in what makes a chassis work, and so you can’t always just go by the OD of the frame. I’ve never run a CRG, so I can’t give you a definitive answer, sadly.