At wigan he often had 3 CBs behind him so a bit more defensive solidity ( at least in theory!). From the games I've seen for Ireland he's sometimes been played more as a 10 or at least with less defensive responsibility with the other midfielders covering him. Ideally it is something he'll develop but not too stressed if he doesn't - we have lots of attacking intent on other areas of the pitch including fullbacks. He's saved so many games with a last minute slide tackle that add up to far more than a couple of goals the other end of the pitch.I think Besic's development will alleviate McCarthy to get forward more than Barry playing further back in the holding/middle 'cb' role.
On your first point though: yes, he does have a lot to think about and weigh up before he can make the decision to get on the ball and stride foreword, definitely. But he's been here over 12 months and I can barely think of more than a handful of times he's stepped up with real intent. He must have had a lot more opportunities than that to carry the ball. It's seems strange to use the word timid with regard to McCarthy - but he is in terms of having the confidence to turn away from a sideways pass and be more direct with a forward run. At Wigan he did it more than he has here (and he does it with RoI), so there's no question he has it in his locker.
Also think he's a but nervous