First set:
1. Flows better. Therotically more fuel economy in the city yet more HP up top where we need flow.
2. Probably.
Second:
1) Should be fairly close. Has a lot to do with the tune and your driving habits though.
2) Cam will cost you 700-800 if you install yourself. Thats for a VS cam, L76 springs, LS1 retainers, new valve seals, new stock chain/tensioner, gaskets and fluids. You may also want new stock lifters (look for a set of OEM LS7 lifters) and new stock pushrods.
3) You'll want an in car tune with a cam. Especially if you'd like to play with the pulley.
Also gives reason to avoid open cone and have some amount of tubing between your air filter and MAF to reduce turbulence.