One Block Wonder is a name coined by Maxine Rosenthal, who wrote the One-Block Wonder books. These are either hexagonal blocks (which fit together naturally) or octagonal ones with corners added to make them into squares so they can fit together. Previous quilts that used the stack-then-cut method were called stack-n-whack, a term coined by Bethany Reynolds for her books.
OBW blocks could theoretically be any size, but in reality they are usually fairly small. The strips are usually cut at **about** 3 3/4 inches, which means that the finished hexagon (if that is what you're using) is only 7 inches.
If you're going to be quilting a king, especially as your first quilt, I would strongly recommend that you check out Marti Michell's book on Machine Quilting in Sections. It is much easier to work in sections on a big quilt on a DSM, and this book explains several methods for doing that, and tells you why and when to use each method. If you want to quilt in sections, you need to make that decision before you sew all the blocks together for your top.
Welcome to this wonderful hobby!
Edited to say - search on this forum for OBW. They do not have to be small quilts. They do not consist of just one block in the entire quilt, but rather there is one *type* of block (hexagonal or octagonal) and one fabric typically in the quilt.