The best person to talk to about your engine is in the glow engine factory support-OS. Bill Baxter. Bill will tell you everything you need to know that you can't find in your owners manual. I'm old school and don't pay a lot of attention to break in. I run the engine until it will idle and transition correctly then go fly with it. I do a lot of vertical maneuvers like BIG open sky loops and stall turns. The old way of thinking is the engine heats up on the up line and cools down on the down line. About 8 or 10 years ago people started getting deep into the break in. My OS and YS engines have been with me for ages and just keep running. I moved 7 years ago and no longer even have a run in stand at the new house. When I had one I used it for test running engines after a rebuild before they went into a plane. Only engines I break in are the SK two strokes but they are another story.
Prop selection has a lot to do with the plane and type of flying you do, one size does not fit all. I used a 16X4 on a OS .91 on a Kaos and it worked very well for how I fly but I liked it more with the 15X6. Some of my planes I used the 14 inch, either a 4, 6 or 8 pitch. Testing is the only way you will ever know what prop works best for you with your engine/plane combo.