That is definitely possible! Most of the choices related to the MC's hobbies, talents, interests, and what they focus on education/career-wise are very direct and unsubtle. The game will generally just present a choice where the player directly picks what they want for those types of traits. And those choices intentionally don't impact Cove. All it does is collect info on you. So you can decide freely and not worry about whether it'll mess up your future Cove. His sporty-studious stuff is set entirely separately.
As for the personality combo you want- there are happy MC options that make him more outgoing, cheerful options that make him more reserved, and friendly choices that leave him as he is. So you can be cheerful person who ends up with a cold Cove. The tricky part is figuring out how to do that. The choices that do impact Cove aren't direct and it can be quite hard to tell what you'll get. A tip is that Cove can become quiet with a cheery MC if he's coddled by them. If they're always there to tell him it's okay and to stand up for him and to do things for him and to be his only company.