There is no one species that you can depend on being tamer then the rest.
It depends on several things, how they were treated before you got them,
how well they like their environment, how you treat them, etc.
Veileds tend to be very aggressive and territorial, most ppl who say their cham
is mean and nasty, turns out it's a veiled. But as always, there are exceptions.
Both my veiled are very tame.
Jax tend to be laid back and docile, and they don't hiss and gape at you.
Panthers are also docile, but can flair up like a veiled if upset.
If you get a young cham that is used to being handled and being close to
ppl, your chances are better that when you get him, he will already be fairly
tame. But it depends on how well they like there new home, and you!
If you want a tame cham, you can ask the breeder for a older cham that has
completely gotten used to being held. Like 5 or 6 months old.
Just tell the breeder you want one that is people friendly.
It will probably be a panther, but no way to tell.
Buy your cham from a small breeder, who does it for the love of their chams,
and not just for a living.