I love applique, do needle turn, find it relaxing. As some of you know, Baltimore Album is my favorite. I'm currently doing 24 lighthouses for my son & his wife, they want to make a drape for their family room from them.
I have done needle turn for over 40 years, have found that the needle is extremely important. I use a long fine sharp. Clipping, trimming seam allowance will help to have a smooth turn. Using the side off the needle to smooth the turned edge under will help to prevent fraying. I usually trim only about 1" in front of where I am working, trim to 1/8th or 1/16" and then turn. This will give you a smooth edge with no puckering. It does take practice, and I have found that the more you do the better one will get.
I love the portability of applique, I take something with me no matter where I go. I have little kits put together with, thimble, scissors, thread, etc. all ready to go.