Speaking of the GX width, I have a pair mounted with 35c Herse Bon Jon Pass Extralights which measure out to 37.85mm. The tire sidewall flares out from the rim ever so slightly, and really seems pretty close to an ideal width for a performance-centric tire on that i24 rim.
Of course it’ll carry a much wider tire no-problem, and I think Jan Heine says a more bulbous tire profile is not an issue when coupled with width, which my limited experience running i23s x 47c substantiates, but I’m hedging my bets with i24 x 35c for when the speeds ramp up and lateral forces increase. I’ve not ridden the Spinergy yet, though, so we’ll see if that proves to be true.
35c Bon Jon Pass on i24 Spinergy GX wheel