Moto G / Nexus 5 Study Abroad Phone?

Hello!

I am going to be studying abroad in Hong Kong / Taiwan in the next year and I am currently trying to determine what phone I am going to be bringing with me abroad. I have three questions:

1. Any personal cell provider recommendations in Hong Kong / Taiwan?

2. Would the Moto G and/or the Nexus 5 be a good choice? The Moto G only has 3G, which shouldn't be a big issue. The Moto G seems to support a lot of frequencies. Getting the Nexus 5 would be good because I would be able to use the LTE when I get back to the states.

3. By purchasing the Moto G or Nexus 5 straight from Google, it will already be unlocked correct?

Thanks!