Though I only watch playthroughs, I can wholeheartedly say that Elio's an <Anemo> user by default. It pretty much fits into his freedom and independence schtick that he has goin' on since childhood (even if it's pushed onto him by his oldest brother), which he inevitably achieved post-graduation. Not to mention it emboldens the carefree and adventurous parts of his personality.

As a swordsman, his weapon of choice is a <Sword>. Not to mention, he would be a five-star (⭐⭐⭐⭐⭐) character.