Yes, this is the whole purpose of EmuNAND. It allows you to retain a low firmware on your Switch, or SysNAND, while enjoying all of the benefits of being on the latest firmware using EmuNAND, which is an emulated NAND partition that is being ran off your SD card. Just be aware that if you use any hacks on EmuNAND, you run the risk of getting banned. Its not a guarantee you may be banned, but its a risk to definitely be aware of.
Likely yes, definitely stay on 1.0.0.
Thanks for the explanations, EmuNAND sounds like it would have the ability to solve any issues of staying on an older firmware. I suppose I will just have to be patient.