SIM for live streaming in Honolulu

Hi there, I'm Matteo and I'm gonna travel to Honolulu soon.. I saw many SIM from T-Mobile online which say "unlimited data", my main question is: are those data really unlimited? I'm a streamer and I'm gonna make some live from Honolulu so I need a sim/plan that allows me to use a lot of giga per day without any limit.. Does T-Mobile plans that says "unlimited" have Fair Use Policy where if you use x giga then you get your internet speed slowed? Or you can just use as many giga as you want per day until you just run out of giga? If so, I can easily buy one of this sim at the airport or I'm supposed to buy it before my departure? It requires a lot of time for the activation?
Thanks :)