procomp wheel ?

Ok, so i've read over threads here and i am a little confused, so i need some help from some fellow tw members.

I have an 05' sport, but i want to buy the procomp 7032's in a 16x8, so i am actually downsizing from my 17 sport wheel. From my understanding the procomp alloy spoked wheels in a 16 (like the 7032) will fit fine...Right?

secondly, why do they make this such a big deal with getting the proper lug nuts? Im getting such a headache trying to figure out the right ones. Ive seen the one wheelers offroad has..so are the extended spline drive the right ones for the 7032 wheel? I know the factory lug nuts dont work, but i dont want to get a lug nut that has TOO much extension past the tapered part as to where i cant torque down the lug nut all the way enough to hold the wheel tight on the hub....which lug do i need???