It very much depends on the subject. Mix of professional, friend, and like a child talking to a parental figure (but not the way I talk to my actual parents. With them I'm an adult talking to an adult. Even as a kid I wasn't this same type of childishly vulnerable and looking for reassurance from my parents)

If it's about my work or practical matters, it's more professional. If I'm talking about my issues in like a more emotionally detached way it's the same half joking/self deprecating tone I take with friends. When we get to something I'm vulnerable about that's when I'm childish.
Sometimes there's also like a petulant child feel to it if I'm upset and hurt. But that's also something I never really used with my own parents because it's childish and immature and not constructive.