It's sort of both. He's a bullied kid who is small and wears glasses, but doesn't actually do anything nerdy or have any nerdy character traits, then he becomes a jock almost accidentally by discovering a hidden talent for wizard football. So he's not a "mean jock" who looks down on nerdy kids or tries to be a tough guy or anything, but he also doesn't have any nerdy traits that could be potentially off-putting to the audience, only surface level aesthetic stuff like wearing glasses and being bullied by his cousin.