Where's the SD card on Nexus 5?

Background story:

Yesterday, YouTube app wasn't working, so I made a Titanium Backup and Nandroid backup. I went to "Factory reset" and assuming Google is sane, and still only reset the internal storage not the emulated SD card, I proceeded with the reset expecting to be met with a tick field to choose whether or not to wipe the SD card. Surprisingly, my expectations weren't met. So turning on my phone afterwards revealed the hard truth... the very hard truth. I lost everything. The damn thing wiped the SD card as well.

Question:

Now to the question, after accepting what happened, I'm now in the process of restoring everything from scratch. Though I see that some apps are storing their data on /storage/emulated/legacy/ directory and others are choosing /storage/emulated/0/... I remember I always used storage/emulated/0 before the accident. So I want to confirm, which of the two is the emulated EXTERNAL SD card? Where do I store my "Data" stuff?

Clarification:

Here's the folder structure: /storage/ has /storage/emulated/ AND /storage/sdcard0 (shortcut)

/storage/emulated/ has /storage/emulated/0 AND /storage/emulated/legacy

/storage/emulated/0 has /storage/emulated/0/(folders include another 0 and also regular SD card files). Accessing the second /0/ shows clockworkmod/

/storage/emulated/legacy has has /storage/emulated/legacy/(folders include another 0 and also regular SD card files). Accessing the second /0/ shows clockworkmod/

So legacy and 0 has the same inside folders. Deleting one file also deletes it from the other. So what's the difference?

info:

Nexus 5, KitKat 4.4, Rooted, CWM recovery