I'm not sure what the stitch has to do with ease in clothing items... Thread is thread and will not stretch unless you use specialty threads that are designed to stretch. It doesn't matter if you use a straight stitch, a zigzag, or a cover stitch.
The give in clothing comes from "ease". This is achieved mostly with curved piecing, but can also come from stretchy fabrics. If you have one piece of fabric that is supposed to be sewn to another piece of fabric, but it's bigger, you have to "ease in" the excess fabric. This creates give in the finished garment.
I've made many, many items of clothing on my Brother 1500, which is not an antique.