Well, I already read about this stuff in the internet but didn't find an answer considering the current system configurations with miiverse NID and stuff. So here I go...
The fact is that I have 2 3DS XL, one that you could call my main with all my games, my nintendo ID (the same I use in my Wii U) and stuff.
The other I bought more for collection, one that came with Mario Kart 7 pré-installed.
The thing is I already have MK7 in my main and therefore to have the game there is kind of a waste. So I was thinking of giving my spare 3DS XL to my girlfriend who has only a normal 3DS.
The thing is, while my spare XL (with MK7) has no Nintendo ID nor did it ever connect to the e-shop, hers already has an NID, miiverse and stuff bought online.
I have read around the internet that if I transfer an system to another which has e-shop stuff, both e-shop accounts would merge and end up making her account get MK7. Is that right even with the NID? As I already said the XL with MK7 has no NID, if it had, would it interfere?
And another point. If by any reason she doesn't want the XL model (as I know she likes the portability of the smaller one) could I do the transfer (just to give MK7 that I know she loves) and then back so to merge the accounts and then send it all back to the original device?