@Draxzelex I haven't been keeping up to date with firmware changes since 8.1. Are there any issues or tips that I should be aware of before I update to 9.2? (you recommended 9.2 instead of the latest firmware 10.0.3 but I'm not sure why)
There's no reason not to update to 10.0.3/10.0.4. You're going to have to update to 10.0+ eventually to play newer games anyway.
For example, I remember you mentioned that nogc is enabled in later firmware updates because there's a game cart update that prevents users from using the game cart with lower firmware if they downgrade.
The nogc patch will prevent the game card slot from being updated, but it will also render the slot temporarily useless. If you update the slot, then it will only work on that system version or newer, however, which is why the nogc patch is enabled by default on Atmosphere if it detects a lower fuse count.
My personal opinion on the matter is that you're probably never going to downgrade your console anyway, so if you use cartridges, you might as well update the slot. If one were to downgrade, it would be to take advantage of a new exploit, which would likely be used to boot an updated emuNAND anyway, where the cartridge would be used.
Also, I'm not familiar with how to install emuMMC. I've been using sysnand with homebrew and offline backups all this time so how can I clean my sysnand for official use and migrate existing games/data to emuMMC?
Do you have a NAND backup from before you started using CFW, homebrew, and game backups? If not, then it might be impossible to restore your sysNAND to a clean state. There are other methods, but they carry more risk than restoring a clean backup, especially since they can result in a log mismatch.
Also, have you been using 90DNS and/or Incognito since using CFW, homebrew, and backups? If not, you're likely banned or flagged to be banned already.