Well what you're asking for does not exist. Or at least not in one guide. Majority, if not all, guides on emuMMC involve setting it up. The process of setting it up is meant to teach you what to expect after you combine it with what you already know about basic Switch hacking.
For example, there are multiple ways of updating sysMMC without burning fuses. The easiest method involves using the homebrew application ChoiDujourNX. Another method involves manually rebooting into RCM after the system update finishes installing. Lastly, you can update while running CFW and having AutoRCM enabled in order to preserve AutoRCM during the system update which will prevent fuses from being burnt. But each of these methods have their own guide.
Switching is self-explanatory. You either reboot or turn off the console and boot into either sysMMC or emuMMC depending on the situation.
If you wipe everything from your SD card, you cannot restore your games; you would have to reinstall them.
And if you're using emuMMC as a ban shield, the goal is to never go online while using CFW & homebrew.