Cellular means the LTE version; there is no phone enabled version. The second one is the wifi version.
I use mine with 8sms for sms and mms. I had to root and use the xposed module to allow texts. It works great but I still sometimes also get texts as push messages.
For voice I use Vonage for outgoing calls and my carrier's visual voicemail app. No incoming calls but I don't get a lot of them. If it's a call heavy day I'll just keep the sim in my Note 2 (my default phone) or my Nokia 520. The 520 and N7 is a sweet pair- lots of options and fairly easy to swap the sim between. Also, they only cost $250 for the two of them, less than the Note 2!
T-Mobile Note 2, unlocked AT&T Note 8, LTE Nexus 7