Depending on what point of time you've met him, Elio would give off different vibes:

Childhood: Slightly curious and observant yet distant due to emotional absence. Unintentionally frightens most people since he also had a tendency of popping out of nowhere at inconvenient times via his unconscious masking of both his presence and Aura, his lack of light in his eyes, his somewhat monotonous tone whenever he spoke, and being a bit too smart and mature for his given age. Basically one of those creepy ghost children you'd see in horror movies.

Adolescence: Discovering himself, you could tell he's more expressive and curious; gains a slight degree of immaturity, but is still the most responsible and dependable one of the bunch. Also strongly opinionated and not afraid to showcase his talents. Though socially awkward, he's putting in much more effort than before since he wants to connect with others. Willing to go along with the whims of others not out of obligation but rather if it's either fun or quid pro quo. Typically his hatred for Pokemon Hunters is obvious, albeit one could feel a sense of bloodlust that's uncharacteristic for a kid his age, which additionally gives Elio a lingering creepy factor from his previous self - albeit, it's more unintentional since he's doing his best to better himself.

High School: After his "education" on Ardyn's recommendation and forced regression in the face of self-sacrifice and desire for power due to his burning hatred for Pokemon Hunters, you could tell he's more confused and conflicted, suffering major trauma and losing a good deal of innocence in the process. Is a bit too self-sacrificial for his own good. Someone that's trying his best to be normal and fit in while also doing his utmost to live up to the expectations of others. However, in the case of the latter, it gives him an amplified "cool factor" since most of what he does easily impresses those around him and unintentionally draws them in. However, his social awkwardness tends to get in the way, but due to his developing handsomeness, he's labeled "Adorkable". He's more or less the "silent protagonist", as he only spoke when needed or communicated through sign language when anxiety hit. Would later grow out of this vibe by the end of his third year, developing into a 'Super cool senior that bedazzles others' - as described by most of his juniors, fellow classmates, and ever-growing followers.

Present-Day: 'Big brother' vibes all-around; though he's super chill, laidback, playful, free-spirited, and mostly smiling, you could unconsciously tell that he's a very open, dependable, and supportive person. Unexpectedly, betraying his physical age - you'd be caught off guard by how sagely he could be at times, especially in his perceptions of life and expansive yet well-grounded knowledge on multiple topics not normally associated with trainers and coordinators. Basically, Elio's personage matches his namesake to a 'T' - being bright and warm like the sun itself; this aspect is played with to certain degrees in that whenever he smiles, it metaphorically blinds others to a certain degree, being "too bright to look at" - which additionally gives off an air of purity and naivety unlike any other (https://v17.mkklcdnv6tempv5.com/img/tab_17/03/28/64/gm984221/chapter_7_resolution/20-o.jpg). Still has his fair share of lingering insecurities, but he's excellent at hiding them to the point that no one would ever notice outside of his family and those in his friend circle.