Try using bullet points or number your questions so I can answer them in order.
As I said, if your console is patched, then the firmware is irrelevant as the exploit is based on the hardware of the console.
emuMMC is short for emulated eMMC. The eMMC is the internal memory of your console and what it runs on. Terms such as "sysNAND" or "emuNAND" are not technically correct as the Switch does not use a NAND chip so the correct terms would be sysMMC and emuMMC but to keep things simple, emuNAND and emuMMC are interchangeable.
You do install CFW on the Switch. CFW is merely ran from the SD card when you launch a payload from RCM. You will understand more of what I'm talking about once you setup CFW. As for the best guide, this is the only one I know of that not only helps you with CFW but also emuMMC.
That jig is fine. There is no "best" jig.
And to repeat myself again, it does not matter whether you use sysMMC or emuMMC for CFW. Its personal preference; there is no right or wrong answer.
Iv'e heard you can still play online as long as you actually own the game and won't be banned. Is this true?