The shortcuts are separate, regardless of whether you've bought the Premium or not. You do get access to the ability to pay $6.99 just to unlock a majority of a classes weapons that could be done by playing the game normally. It's not even really pay to win, though, because you still have to get kills with said weapons to unlock the scopes, barrels and bipods that enable them to be more specialized in their duty. I almost loathe getting a new sniper rifle, due to the fact that it'll start with just a 8x or so scope after I've been attached to a lesser one with a 12x scope and bipod, which increases my ability to snipe drastically by giving me longer range and complete stability when stationary.
I suppose the reason I do extremely well one game and extremely badly another is because of the difficulty difference, in a way. There's no real way to gauge the skills of the players you're about to face or be paired with, so one game you might have the support of decent players and the next the game could team you against a full roundup of level 100 players. Not that they're invincible, but they do tend to be better.
As a side note, I kinda like CQC in small doses. It has a different feel to it. I suppose it would be called more Call of Duty-ish, but it does change the tactics and weaponry by such a large degree that you can't play the same way in it as you would in say, Conquest Large. It's also great for racking up points on a Recon, if you can get a T-UGS, since you spot practically everything on half the map. Sniper rifle builds need not apply, though, so use a carbine if you have it globally unlocked.