Creating EmuNand using either Hidden Partition or Files on microSD takes up around 29.1GB, so make sure have a minimum of 64GB SD CARD.
Just be aware that the 29.1GB used for EmuNand is NOT wasted space, just treat this like your internal memory, you can use this free space to install NSP's. Real Nand and EmuNand are separate and DOES NOT talk to each other.
Some Tips:
If your not banned, my personal preference, I recommend to NOT go online when using EmuNand, for most, EmuNand is used to play backups, XCI's and install NSP's while completely offline. If you want to go online with legit games, access the eShop or purchase a online subscription, do this in Real Nand, in saying that, there are people who use EmuNand online, since Stealth mode is enabled by default and also people use blocking DNS as well, they have not been banned, while others have, the risk is to high. if you want to minimise the risk of being banned, best to stay offline in EmuNand.
Before created EmuNand, boot normally into your Real Nand, delete any/all of your internet settings. When you create an EmuNand, it is an exact CLONE of your Real Nand, since you don't have any internet setting, you wont accidentally go online.
Also change the theme to DARK mode in EmuNand and leave Real Nand in White, that way, you know which NAND you are in.
If you decide to go online on Real Nand, make sure you NAND is clean, meaning, do not access CFW or access any Homebrew apps, if you do, your system will most likely be flagged, once you go online your logs will be sent to Nintendo and you may/will/eventually get banned, either straight away or at a later date. Some are on CFW and have been going online for months and still have not been banned, there is no 100% info as to what triggers a ban but the most obvious for those that got banned is accessing CFW.