Congratulation on your new purchase. For the telematics, all 2016+ Leaf has 3G radio, Nissan offer free upgrade for the 2015 model year. All 2014 and earlier model will have to pay to upgrade. You can check the version number in the setting and it will tell you if it has a 3G radio, someone has post instruction on how to check this in the MNL, you can search for it.
Nissan uses the AT&T for the cellular service for the Leaf, so how well it works will depends on the AT&T cellular strength in your area. The AT&T cell reception is pretty bad at where I live. If I park the car just one parking space over, the telematic will stop working. It is a nice feature, I use it quite often to check the SOC and to turn on climate control before taking kids to school.
2019 Leaf SV PLUS Pearl White, leased on Sep 2019
2017 Leaf SV Glacier White, leased on May 2017
2016 Leaf SV Gunmetal Grey, leased on May 2016, Sold to Carvana
2013 Leaf S + quick charge package, leased on Feb 2014, returned Feb 2017