Wet Nitrous Kit - mix nitrous & fuel and spray through a fogger nozzle. Can either be single nozzle, two, or one per cylinder (direct port)
Dry Nitrous Kit - only inject nitrous through a fan spray or fogger nozzle. Some dry kits use manipulation of the vehicles fuel pressure regulator to injects the rail fuel pressure and deliver more fuel via stock injectors. More pressure = more fuel. Some newer vehicle like 4.6 liter Mustang and Gen III GM V8s allow you to inject nitrous before the vehicles mass air flow sensor and the vehicle computer interprets and adds the extra fuel
Dry kits are cheaper and easier to install. I would usually recommend then for people looks for a decent bang 4 the buck and someone looking to stay under 100-125 hp. Wet kits are a bit harder to install, however they can be fine tuned more than a dry kit can. Both are great.
Low mileage and high mileage isn’t so much a factor as the condition of the vehicles engine. The main thing about nitrous is you can’t get greedy and surpass the mechanical limits of your engine. Nitrous does stress parts just like a turbo or any other power modification would. As long as the nitrous is tuned right and running at a safe and proper A/F you will not have a problem as long as you are reasonable. If you have any other questions please give me a call or email