Thx for the reply, I guess I can see the full picture now. So I just need to make sure my NAND is clean (make a backup if I want to, and I'm obviously going to), create emunand hidden partition or file, and if I want to switch between CFW and OFW I just need to select "Boot CFW" or "Boot OFW" from SX OS menu? I might have confused myself with this two SD cards thing, it's because people say "you should use one sd card for acessing CFW and one for OFW". I think it makes sense now, it means that I should create emunand and when I want to boot OFW online, I should swap my sd card with another one without CFW stuff, right?
I didn't know that Nintendo doesn't have the right to scan SD cards, weird. I may as well end up choosing the "file" emunand.