So I signed up for a Simple Choice plan for $50/mo. They're having a sale on SIMs, so that cost me $0.99. I told them 10 times I was planning on canceling within a month, which they said was ok, so long as I pay for the month I used. I verified that the international texts and data are free, which they are.
Also, I just have a basic phone, so I won't be able to test out wifi anything. I don't have an unlocked smartphone, but if someone knows of a cheap one I might consider it. Also, even if I do get one, I'm not sure T-Mobile's wifi calling applies on all phones with wifi or only on their phones.
I'll let you know when I cancel how smoothly it goes.