it does not use boot2, when you install bootmii on NAND, it is installed so that, when Boot2 is lauched by Boot1, bootmii code runs first. So, technically, it uses boot1 ability to launch boot2 (and that's why bootmii doesn't work if your Wii has the last boot1 version).
Once running and being loaded (from NAND remember), it does not use the NAND anymore unless:
1/ you ask Bootmii to backup/restore your NAND
2/ you leave bootmii to launch the system menu or the homebrew channel
But this is the same for EVERY Wii legit applications, once they are loaded from NAND into CPU memory (RAM), they don't use the NAND anymore until they need to access it to retrieve some data or to load others programs.
That's why your question does not make many sense, without the NAND, nothing could be run on your Wii.