All of your keys can be the same width, or they can be a variety of widths, the length can be any length that works for the quilt they are going on, no rules. I've done them with strips ranging from 3/4" wide up to 2 1/2" wide, everything in between. I've had some that were 2 1/2" long, some that were 8" long. I've used jelly rolls & made them all 2 1/2" wide. I made them scrappy with every fabric in the quilt and I've made them with just 2 fabrics. I've always added the two sides then top & bottom.I have mitered the corners most often, but if the strips were all different random widths, scrappy I either used corner blocks or boxed the ends. Anyway you like is fine