Adam generally identifies as straight. If he develops feelings for you, he'd say "straight, but with an exception for Chris".

He's something like a 1 or 2 on the Kinsey scale.

If you pressured him on it, he'd probably say bisexual, but wouldn't be comfortable with the label. "Sapiosexual" would probably be a better label, with Carlos' coming out helping him realize that the admiration he has for Chris might be more than just admiration.

I'd've guessed  heterosexual/demi-homosexual. (Trying to figure out whether this aspect of Adam was a romance trope or something that occurred in reality led me to some useful personal realizations.)