I have made 2 DWR using Quilting from the Heartland templates. I did not use any type of interfacing, personally I feel that would add bulk... depending on the sizeof quilt you were making
I have never seen the templates you are going to use, but the templates that I had there really was not much problem at all with the curves. The pieces were small and curves were gentle. I am sure I will make a few more DWR going forward because the ones that I did went so well
good luck and have fun!