For the most part, you will need to follow the changelog and the forum. There's no easy way to know what the differences are between the various builds, let alone 2 builds with 6 months difference between them.
As for the MySQL/php question, I personally have switched between Edge and the other builds a number of times now (and currently on 11.0-EDGE_485) and have yet to experience cPanel or WHM updating them for me without my consent. All I had to do was add an exempt into the up2date and yum conf files to not update either of these, and all is well. This allows me to specify right in the WHM settings which version of each I want, and allows me to update them at my convenience, instead of at cPanel's decision to include them into the build.