Dry kits are safe to 75 shot with added fuel pressure, a good pump, cold plugs, and your timing slightly retarded (3-4 degress).

Wet kits are safer but require more tuning.

Venom currently only offers a Dry kit, Zex offers a Dry (what I have) and recently a wet kit.

You only want to inject nitrous at WOT and with the engine under load (in gear). A Direct Port system is used only when you want as potent a shot of Nitrous as possible. If you are not going over 100 Shot then it's not worth the investment. A Wet or Dry Intake mount kit works just fine.

Why would you want to "hit it" before you started driving?

I assume you mean a purge system. The classic nitrous gas spraying up the windshield? You can add that to any kit. Basicly you use it once when you open your bottle to make sure the nitrous lin is full of only nitrous and no air and then when you close your bottle to pruge out any nitrous left in the system.