I say 13m edge will be a good interface between 19 speed and 10 cat. Its not a wave kite but it is way better upwind in the lighter airs, awesome jumping and gliding, you can ride down the line looping it. It will be a shit ton better than the speed in the waves.
I've got a 13m Edge and I feel it's the worst kite you can get for strapless wave riding. It turns slow, needs speed to pull, and then when it does start pulling it pulls too much and yanks you right off the wave. It does great for hangtime and for going upwind, but I think almost anything else is better for strapless wave riding.
I also ride Rebels. They retain most of the upwind and jumping benefits of the Edge although a bit less, but they are MUCH more fun to ride in the waves with a strapless board. The Rebel is more of an all around kite and ticks a lot of boxes (as do quite a few other kites).
If strapless is all you want to do though, go for a surf kite like a Drifter, Cabo, Pivot etc.