Go wild! As much as he passes for human physically (technopath-to-speech-ing aside), Ghost is very definitely not. He's a big psychic presence (even the least advanced Typhon are psychically "bigger" than humans on the noetic field, that's Prey canon, and Ghost is significantly more advanced than a Mimic), though it's up to you how you want that to translate.

More detailedly, his age will probably register as either "30" or "that's an infant" or both, probably not even consistently, he's pretty powerful and just a bit eldritch-alien, and in good health, but the kind of "in good health" where you can tell that his definition of good health isn't quite the same as human baseline.