#64
I find it best to have the assault rifle, pistol etc all set to third-person view when aiming (and leave the sniper to use first person) - because as you say, it seems to be quite jarring and take a while to focus on an enemy in the heat of battle with first person sights. You should give it a go - I think it's the "ALT" key when aiming. Luckily the game seems to remember what weapons you use like this, so the sniper will still use first person scope.
As for the "handling" question, I have no idea.