When I brought my Samsung S7 with a Fi data sim to Korea, it worked fine. When I brought it to Japan, nothing. My Nexus 5X worked great in both places.
I believe that's because there US S7 doesn't have the LTE receiver for the data band used in Japan, whereas the 5X does and not the issue of the Fi SIM. I bet if you got an S7 from Japan it would have worked fine
