It isn’t about the character you choose to use for the race. I’d be more concerned about the 50cc part. Although, now that you mention it, it seems like using bigger characters (Bowser, etc) made the car move slower.
Want to feel older? Since the N64, we've had the GameCube, Wii, Wii U and Switch. The latter of which has been out for 7 years already and is probably going to be replaced soon.