Misc NNID issue/question?

[2DSGamerdude]

hay, guys
I have a question regarding Nintendo ID:

I made the nintendo ID using my old 3DS (which was OFW on sysnand at the Time)
and I was able to get in to my account to change the email to use on switch.
(when it was CFW'd) through my emunand (unlinked).

my problem here is that if I remove the SD card with emunand on it from the 3ds, and format the system (offline)
since my NNID is linked to my nintendo account on switch,
will getting rid of my old 3ds that I had made the NNID (sell the system)
remove my nnid or cause any problems?

also, is an NNID really needed for switch or nintendo account?
what is an NNID used for on switch?
and if I don't have it, what do I lose if I remove it?

also, is my old system if I sell it to a friend of mine, tied to my NNID or once I formatted the system, the ID stopped working for said system?
I changed the access of my NNID to "pc usage".

thanx.

 

[dubsmachine]

I sold my 3ds two years ago and it was linked to my NNID.
I bought a new 2DS XL this week and thought I could just sign in and download everything from my previous life on the 3DS.
Oh no it's not so simple.

However I emailed Nintendo support and explained that I sold my old system and now have a new one and want to unlink my NNID from the old system so I can link to the new one.
They replied the next morning, asked some questions (3 games that I downloaded was hardest) then 5pm that day they emailed that they had unlinked my NNID and old 3ds.

I then logged into the NNID on my new 2DS XL and suprised myself when i saw all the games I had downloaded in the past and very happy they are able to be re-downloaded so I don't have to pay for them again.

So yes NNID is needed but you don't need to transfer from old to new unit at the same time as the myth has you believe - follow the link on Nintendo support > NNID and they will do it for you in less than 12 hours in my case.