Let me chime in since I've done lots of reading on the different kits.
You may also read info from Dave Neibert, as he's got plenty of experience with N2O on a SC. So I would search posts for nitrous with Dave Neibert...
First off, the dry nitous kit, NOS brand or ZEX will increase fuel pressure to the FPR (fuel pressure regualtor). This is the same thing that happens with the supercharger. The boost pressure leans on the FPR for more fuel during boost. The problem with the dry kit is that you may be close to maxing out the injectors. I've read somewhere here that once the fuel pressure gets past 50 PSI, the the injectors may freeze up; stock pressure is about 40 lbs and increases about pound for pound with boost. It may be like 39lbs, but you get the idea. So with the nitrous and boost increasing fuel pressure, it may get close ot the limit of the injectors.
I haven't delt with Zex, but if you call the NOS tech folks, they will tell you not to use a dry kit on a forced induction app... I know people are using the dry setup, but according to the NOS folks, they are runnig them on the edge of injector failure...
Now the wet vs dry setup in regards to what RPM is required, the N/A guys must be at a certain RPM (3000???) for the wet setup because the fuel can drop out and casue a nitrous backfire at low RPM. To my understanding, in a turbo/blown application, this is a non-issue, as the boost doesn't allow the fuel to dropout at low RPM as it would in a N/A application, and for smaller shots, say below 100, a nitrous backfire is alot less likely anyways. The wet kit is also more tunable as well.
I know Dave Neibert uses a 100 shot in his 11 second SC, and I'm pretty sure he hits it off the line as well, but you may want to check with him to get details of his setup.
In any case with nitorus, a wideband O2 setup is almost a must to make sure you aren't leaning out.
AS for nozle location, dry vs wet don't matter; what matters is that if it is plumbed in the lower IC tube, (before the ACT sensor) the computer will advance timing due to the reduced temps. If plumbed in the return plenum after the sensor, the computer will ignore the shot, thereby NOT advancing timing.
The NOS systems general rule of thumb is to reduce timing 2 degrees per 50 HP of nitrous. IIRC, the eec will pull a max of 4 degrees of timing based on ACT temps, and a warmed up SC at WOT will surely be retarded the full 4 degrees at WOT. So if you add nitrous before the ACT, the computer will probably advance the timing those 4 degrees instantly, which may be bad, particularly on a 100 shot where timing should be retarded 4 degrees.
So the general rule, is to plumb it into the return plenum, after the ACT sensor to keep the timing correct.
Also, pulling the octane plug will retard timing by 4 degrees also, so if you think your motor is up to a 100HP shot, pulling the octane plug should retard the timing the required 4 degrees.
I would not run nitrous without a wideband O2 meter, and I would start small, say 50HP and go form there. This is what I plan to do in the next month or so as a matter of fact. I'm gonna see if my current old motor will hold up to a well-tuned 100 shot
Anyways, there's my 2 cents.