1) I don't use nurbs all that much, and when I do, I do not boolean, so I'm not 100% sure, but I'm pretty sure that a nurbs boolean creates a trimmed object.
2) Trimmed surfaces can be animatd, but they cannot be deformed in most cases. For example, you can use them to make a car. A car animates rigidly, without deforming parts. I'd probably not use trimmed surfaces with a character, though.