I used 1" strips (1/2" finished width) as the outline strips on my celtic knotwork pieced wallhanging. Need to take a picture of it once I get the dowel rods on the back to hold it stretched.
You can also use that width strips as a very narrow flange for framing a block when the background of your print and your sashing would be too close to the same color. Creates a piping type look.
Not sure about trying to use the 1/2" strips except as something for really skinny stems on needleturn applique maybe?