Hello and Welcome :D:D:D
I use wonder under all of the time, but I like the finished look of going around the edges with a blanket stitch.
I would question whether the edges would unravel after a few washings, no matter what brand that you use :D:D:D
If you are going to sew around the silouhettes, I would do it while they are still blocks...it is much easier than trying to do it when the top is put together :wink: The more you handle them, the greater risk of them starting to unravel, too.