In a different thread, people were complaining that Google Fi doesn't let you tether while roaming. Is that false? Or is it just a limitation for certain phones?
Only for iPhones. Androids tether normally. It's due to agreements between Google and the carriers. I was able to tether with an iPhone in Costa Rica, but I've been to 20+ countries with it and it's been only one or two countries where it worked.
With an iPhone you can't tether while roaming. I bought a Huawei LTE router devices and popped in a data sim for when I'm traveling and the speeds are ludicrous. (Like, stream 1080p with zero issues, use 4GB in an hour. Dangerous on my limited plan)