I know Pangaea was a supercontinent that existed 270 million years ago and it started to break apart around 200 million years ago. I'm not clear on whether Pangaea was 1,2, or multiple tectonic plates. Can someone help me?
It was almost certainly multiple. I can't say for 100% but I think it was very very likely - cause of the way they split apart for one.
For example, today: Europe, Asia and in a practical sense, Africa are all connected but contain several different plates. The Indian Plate and the Eurasian plate are 2 different plates but the land is connected, so you'd never know it was two plates - well, except for the frequent earthquakes.
Plate Tectonics is thought to be about 3.2 billion years old: http://sciencenordic.com/modern-plate-tectonics-arose-32-billion-years-ago
Pangaea consisted of all the tectonic plates that are around today including Antarctica, Africa, NA, SA, Australia, Europe, and Asia (am I forgetting any?). No one knows why the continents broke apart but there is plenty of speculation. The best bet is that the convection in the mantle changed. It drives plate tectonics. Where to convective cells well up, rifting occurs. The continents were torn apart in areas that were above these convective cells.