When you get the nitrous kit, it will explain all this in the directions. NX and NOS are very good. But the fuel can be tapped off the end of the fuel rail with an adaptor...Several of our vendors keep them in stock ( try Mcnewsautomotive.com )
The nitrous flow and the fuel flow ( which control the HP ) are controlled by jets that you can change with different sizes. One size larger on the fuel jet makes a slightly less powerful hit, but it is safer on the focus.
When you get the nozzle you will see how it mixxes, the fuel at about 40psi shoots in and the nitrous at 950 psi shoots through the fuel, it does a pretty good job of atomizing it.
YES, after the MAF.
Speed is only a matter of money; how fast do you want to go?