James is perfectly solid, perfectly safe, perfectly nice op. Possibly getting a bit bored by James on here, as it never went out of fashion and now seems to be a never-out-of-fashion-but-currently-very-in-fashion name which it was when I was young, along with Sam and Ben.
Miles I really don't get as being a nice name. It's not weird, it's not teaseable, but to me is as random as calling a child Metre or Kilogram. Sounds a bit like Giles and Nigel to me, neither of which are very attractive imo.
Harrison is a nice sound, but I much prefer the more classic Henry, Harry or Harold. Surname names are to me a bit like place names (think Brooklyn).
Cameron is again not a weird or teaseable name but just rather middle aged man-ish to me, and again has a surname feel. Vaguely makes me think Cameroon, and I don't like the unisex quality.
Connor I don't like. Connor the con man.
Tristan I rather like but I can concede it has a middle class and slightly wet feel, which I think is why, ime, men tend not to like it. It does make me think a little of a boy whose mummy made him wear toddler dungarees a year or two too long BUT there are far worse images than that! Makes me think of a nice boy who possibly has an arty streak - a choirboy maybe. I quite like the Tristan and Isolde medieval feel. The opera may be why I think choirboy.
Of all of them, I'd go with Tristan if wanting to be a bit unusual, James if wanting to be safe, and I'd probably myself choose Harry but for Harold not Harrison.