A:Answer From what I find in forums, 100mb / sec works out to be about 45GB / hour in actual file size. A U1 card might be fast enough, but U3 cards do not cost a lot more. Might be cheap insurance, just to be sure. To answer your exact question, a 128GB card may fall a bit short of your 3 hour mark. The next step up would be 256GB and they are not cheap. One other thing to consider is battery life. The display might say "4 hours of battery" when you start recording, but there are many factors that may reduce that considerably.
As for your other question, all I can do is give an opinion. Using a microSD card with an adapter gives you twice as many electrical connections that could cause problems. I personally would not recommend it.
