Do not use a thick thread or your seams will be too bulky. I use Bottom Line from Superior for my piecing and I love it. It is hard to believe that a single thread thickness makes that much difference, but I promise you - sometimes it can make a BIG difference.
Good luck with your class and just remember that there are about as many ways to quilt and piece as there are quilters and piecers. If you like to something a different way, then do you own thing! The only thing that matters is if you are happy with the result.