The recommendations were to have a fully formatted card before creating the emunand, but I already had 2 partitions on it. Probably that's what messed up SX OS trying to create emunand. As of writing this, I'm giving it another go, now with the micro sd card as clean as it gets. I'll post/edit my results in due time.
If the worst case scenario happens, it is a good idea to have a file-based emunand? I mean, I could always create backups of my save files every now and then, so I don't mind having to install everything should my sd card die. But everywhere I read, people treat having it file-based as a last resort.
Edit: Same error again. I'm doomed to not have an emunand!
Edit2: Out of curiosity, I tried to boot Stock (Sysnand) and is hangs on a black screen. Is my Switch bricked? Or is my nand corrupted?