Is nethunter an app, or ???

Hello guys, I wanted to install Kali Nethunter on my Oneplus 6T. Before starting I read a couple of articles in this site, where it is specified that three versions of nethunter exists:

- Nethunter Rootless which is a core version without root privileges and can be used in your own system like an "app" by using Nethunter app.
- Nethunter Lite which is the advanced version of nethunter rootless but with root privileges but without a custom kernel (always like an app in your own system?).
- Nethunter which is the full os with modified and compiled kernel that can be used to do all things.

My question is, the full Nethunter that I need (because it supports WiFi Injection) can be used as an "app" like Nethunter Rootless, or I have to substitute my own system with the new Nethunter?

Sorry for the dumb question but I didn't find anything that can explain how can I install the full nethunter.