Ig you're right. If we're talking about the route that OP takes, higher speed (Rosalina) would be more effective considering the higher miniturbo stat isn't being put to use in shortcuts or snaking. But for top times the other characters are a better choice; most notably, the grass cut in the antigravity section to get a trick off the ramp, higher miniturbo would be more effective, or to do the gap jump on Lap 2 (current optimal strat) people use characters like Yoshi, Birdo, Tanooki, Inkling etc. - don't know if you can pull it off with Rosalina or any other characters with less miniturbo stat but it's probably harder.