Verizon has world phones, that have some GSM capabilities, they also have SIM cards, because LTE is GSM tech and SIM is part of LTE specs, so yeah it should work at least on some frequencies. The only ROM that has WiFi calling, as far as I know is T-mo. There was some guy claiming he loaded pretty much all different ROM's he could get into his Note and it worked, but don't remember details, do search maybe in International Note 3 forum and see if T-mo is mentioned. Not sure if you care, but right now loading ROM's could trigger Knox flag, so maybe research this before hand and I have a feeling soon we may have some new breakthrough, when loading any ROMS is no problem, but not sure if Knox flag can ever be reversed, once tripped, there is no way for now.
BTW I'm not sure if you're aware, once you have WiFi calling, you can call home from around the World on WiFi for free. Don't let other people call you, but you can make free international calls home as long as you're on WiFI. It does not work for local calls. That is outside the new international calling plan T-mo has.